Unable to uninstall Tensorflow - Folders still remain in dist-packages
Yes, you need to delete it manually, you can follow the below steps to do it.

Go to the site-packages directory where pip is installing your packages in your case usr/local/lib/python3.6/dist-packages/.
You should see the file that corresponds to the package you want to uninstall. Delete the file for your case rm -rf tensor*.
Install your required Tensorflow version pip install tensorflow==1.7

I hope this solves your issue.
I installed tensorflow using sudo pip3.6 install tensorflow==1.7 (I already had tensorflow 1.6 but wanted to upgrade) however I am unable to uninstall it. I tried sudo pip3.6 uninstall tensorflow and it said that tensorflow is successfully uninstalled but I don't think that's true. I get the following error when I try to run a tensorflow python code (which ideally should say import error I guess)

AttributeError: module 'tensorflow.python.training.checkpointable' has no attribute 'CheckpointableBase'

Using sudo pip3.6 uninstall tensorflow again only shows

Skipping tensorflow as it is not installed.

I looked around a little and found the following folders in usr/local/lib/python3.6/dist-packages/

tensorboard
tensorboard-1.7.0.dist-info
tensorflow
tensorflow_datasets
tensorflow_datasets-1.3.2.dist-info
tensorflow_estimator
tensorflow_estimator-1.13.0.dist-info
tensorflow_metadata
tensorflow_metadata-0.21.0.dist-info
tensorflow_tensorboard-0.4.0.dist-info

It seems to be a mess. Can I go ahead and simply delete these folders? What is the correct way to removing these?