Issue title: Exiting zen mode focuses the terminal
 Issue body: <!-- Please search existing issues to avoid creating duplicates. -->
<!-- Also please test using the latest insiders build to make sure your issue has not already been fixed: https://code.visualstudio.com/insiders/ -->

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- VSCode Version: 1.31.1
- OS Version: Ubuntu 18.04

Steps to Reproduce:

1. Open an editor with the terminal open. Put focus in the editor (not the terminal)
2. Enter and then exit zen mode using the keyboard shortcuts or from the command palette
3. The focus is now in the terminal

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Does this issue occur when all extensions are disabled?: No

 Comments: 
 Comment 0: (Experimental duplicate detection)
Thanks for submitting this issue. Please also check if it is already covered by an existing one, like:
- [Can't exit zen mode when restarting vscode (#67059)](https://www.github.com/Microsoft/vscode/issues/67059) <!-- score: 0.623 -->
- [Line numbers don't appear after changing setting while in zen mode. (#68291)](https://www.github.com/Microsoft/vscode/issues/68291) <!-- score: 0.549 -->
- [Zen mode restore setting restores only full-screen (#44652)](https://www.github.com/Microsoft/vscode/issues/44652) <!-- score: 0.538 -->
- [Keyboard shortcut search results for "focus terminal" have odd ordering (#68271)](https://www.github.com/Microsoft/vscode/issues/68271) <!-- score: 0.457 -->
- [Zen mode remove top bar (#30567)](https://www.github.com/Microsoft/vscode/issues/30567) <!-- score: 0.455 -->
<!-- potential_duplicates_comment -->
 Comment 1: You can try the fix in tomorrow's vscode insiders and let us know if it fixes your problem
{'source': 'GithubIssues', 'repo_name_with_owner': 'Microsoft/vscode', 'issue_id': 412023548, 'repo_stars': 77599.0}