Issue title: Can't add product attribute to Images group programatically
 Issue body: ### Preconditions (*)
1. Magento 2.2.6 (haven't tested on 2.2.7 or 2.3)

### Steps to reproduce (*)
1. Create custom attribute programatically, which is to be added to the 'Images' group e.g.:
```
            $eavSetup->addAttribute(
                \Magento\Catalog\Model\Product38d1:d2b4:3d06:83e8:96a5:8c2:893d:aba5NTITY,
                'product_image_attribute',
                [
                    'type' => 'varchar',
                    'label' => 'Product Image Attribute',
                    'input' => 'media_image',
                    'frontend' => 'Magento\Catalog\Model\Product\Attribute\Frontend\Image',
                    'global' => \Magento\Eav\Model\Entity\Attribute\ScopedAttributeInter38d1:d2b4:3d06:83e8:96a5:8c2:893d:aba5SCOPE_STORE,
                    'filterable' => false,
                    'visible_on_front' => false,
                    'used_in_product_listing' => true,
                    'required' => false,
                    'group' => 'Images'
                ]
            );
```

### Expected result (*)
1. The attribute is created and added to the Images group

### Actual result (*)
1. SQL duplication error:
![image](https://user-images.githubusercontent.com/9678552/50009804-c9838700-ffaf-11e8-99ce-d08dbefd49d3.png)


 Comments: 
 Comment 0: Hi @robbie-thompson. Thank you for your report. 
To help us process this issue please make sure that you provided the following information:
- [ ] Summary of the issue
- [ ] Information on your environment
- [ ] Steps to reproduce
- [ ] Expected and actual results

Please make sure that the issue is reproducible on the vanilla Magento instance following **Steps to reproduce**. To deploy vanilla Magento instance on our environment, please, add a comment to the issue: 

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where `$VERSION` is [version tags](https://github.com/magento/magento2/tags) (starting from 2.2.0+) or develop branches (for example: 2.3-develop). 
For more details, please, review the [Magento Contributor Assistant](https://devdocs.magento.com/guides/v2.2/contributor-guide/contributing.html#contributor-assist) documentation.

@robbie-thompson do you confirm that you was able to reproduce the issue on vanilla Magento instance following steps to reproduce?
- [ ] yes
- [ ] no
 Comment 1: @robbie-thompson well, I believe there are some builtin attributes added to Images group, isn't it?
 Comment 2: @orlangur There are a few created in CategorySetup.php: https://github.com/magento/magento2/blob/2.3-develop/app/code/Magento/Catalog/Setup/CategorySetup.php#L603-L613

I've tried creating them the exact same way as shown, but the same errors occurs.
 Comment 3: Hi @developerarun. Thank you for working on this issue. 
In order to make sure that issue has enough information and ready for development, please read and check the following instruction: :point_down:
- [ ] 1. Verify that issue has all the required information. (**Preconditions**, **Steps to reproduce**, **Expected result**, **Actual result**).<details><summary>Details</summary>If the issue has a valid description, the label `Issue: Format is valid` will be added to the issue automatically. Please, edit issue description if needed, until label `Issue: Format is valid` appears.</details>

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</details>

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- [ ] 6. Add label `Issue: Confirmed` once verification is complete. 

- [ ] 7. Make sure that automatic system confirms that report has been added to the backlog.
 Comment 4: Hi @milindsingh. Thank you for working on this issue. 
In order to make sure that issue has enough information and ready for development, please read and check the following instruction: :point_down:
- [ ] 1. Verify that issue has all the required information. (**Preconditions**, **Steps to reproduce**, **Expected result**, **Actual result**).<details><summary>Details</summary>If the issue has a valid description, the label `Issue: Format is valid` will be added to the issue automatically. Please, edit issue description if needed, until label `Issue: Format is valid` appears.</details>

- [ ] 2. Verify that issue has a meaningful description and provides enough information to reproduce the issue. If the report is valid, add `Issue: Clear Description` label to the issue by yourself.

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- [ ] 4. Verify that the issue is reproducible on `2.3-develop` branch<details><summary>Details</summary>- Add the comment `@magento-engcom-team give me 2.3-develop instance` to deploy test instance on Magento infrastructure. <br/> - If the issue is reproducible on `2.3-develop` branch, please, add the label `Reproduced on 2.3.x`.<br/>- If the issue is not reproducible, add your comment that issue is not reproducible and close the issue and **_stop verification process here_**!
</details>

- [ ] 5. Verify that the issue is reproducible on `2.2-develop` branch. <details><summary>Details</summary>- Add the comment `@magento-engcom-team give me 2.2-develop instance` to deploy test instance on Magento infrastructure. <br/>- If the issue is reproducible on `2.2-develop` branch, please add the label `Reproduced on 2.2.x`</details>

- [ ] 6. Add label `Issue: Confirmed` once verification is complete. 

- [ ] 7. Make sure that automatic system confirms that report has been added to the backlog.
 Comment 5: @milindsingh Thank you for verifying the issue.

Unfortunately, not enough information was provided to created internal ticket. Please consider adding the following:
- [ ] Add `"Reproduced on "` label(s) to this ticket based on verification result

Once all required information is added, please add label `"Issue: Confirmed"` again.
Thanks!
 Comment 6: @milindsingh Thank you for verifying the issue. Based on the provided information internal tickets `MAGETWO-97219` were created
 Comment 7: Hi @milindsingh. Thank you for working on this issue. 
Looks like this issue is already verified and confirmed. But if your want to validate it one more time, please, go though the following instruction:
- [ ] 1. Add/Edit `Component: XXXXX` label(s) to the ticket, indicating the components it may be related to.

- [ ] 2. Verify that the issue is reproducible on `2.3-develop` branch<details><summary>Details</summary>- Add the comment `@magento-engcom-team give me 2.3-develop instance` to deploy test instance on Magento infrastructure. <br/> - If the issue is reproducible on `2.3-develop` branch, please, add the label `Reproduced on 2.3.x`.<br/>- If the issue is not reproducible, add your comment that issue is not reproducible and close the issue and **_stop verification process here_**!
</details>

- [ ] 3. Verify that the issue is reproducible on `2.2-develop` branch. <details><summary>Details</summary>- Add the comment `@magento-engcom-team give me 2.2-develop instance` to deploy test instance on Magento infrastructure. <br/>- If the issue is reproducible on `2.2-develop` branch, please add the label `Reproduced on 2.2.x`</details>

- [ ] 4. If the issue is not relevant or is not reproducible any more, feel free to close it.

 Comment 8: Hi @robbie-thompson, based on

> If we add 'group' => 'image-management' , it will create fine because image-management is correct attribute_group_code but 'group' => 'Images' expects attribute_group_name so i can not simply change it.

I make a conclusion that provided code snippet is incorrect. It looks like there is nothing to fix here from core perspective. Please verify if proposed solution works for you.
 Comment 9: Hi @engcom-backlog-nazar. Thank you for working on this issue. 
In order to make sure that issue has enough information and ready for development, please read and check the following instruction: :point_down:
- [ ] 1. Verify that issue has all the required information. (**Preconditions**, **Steps to reproduce**, **Expected result**, **Actual result**).<details><summary>Details</summary>If the issue has a valid description, the label `Issue: Format is valid` will be added to the issue automatically. Please, edit issue description if needed, until label `Issue: Format is valid` appears.</details>

- [ ] 2. Verify that issue has a meaningful description and provides enough information to reproduce the issue. If the report is valid, add `Issue: Clear Description` label to the issue by yourself.

- [ ] 3. Add `Component: XXXXX` label(s) to the ticket, indicating the components it may be related to.
- [ ] 4. Verify that the issue is reproducible on `2.3-develop` branch<details><summary>Details</summary>- Add the comment `@magento-engcom-team give me 2.3-develop instance` to deploy test instance on Magento infrastructure. <br/> - If the issue is reproducible on `2.3-develop` branch, please, add the label `Reproduced on 2.3.x`.<br/>- If the issue is not reproducible, add your comment that issue is not reproducible and close the issue and **_stop verification process here_**!
</details>

- [ ] 5. Verify that the issue is reproducible on `2.2-develop` branch. <details><summary>Details</summary>- Add the comment `@magento-engcom-team give me 2.2-develop instance` to deploy test instance on Magento infrastructure. <br/>- If the issue is reproducible on `2.2-develop` branch, please add the label `Reproduced on 2.2.x`</details>

- [ ] 6. Add label `Issue: Confirmed` once verification is complete. 

- [ ] 7. Make sure that automatic system confirms that report has been added to the backlog.
{'source': 'GithubIssues', 'repo_name_with_owner': 'magento/magento2', 'issue_id': 391146885, 'repo_stars': 10324.0}