[Merge] lp:~nick-dedekind/qtubuntu/1648842.window-focus-regression into lp:qtubuntu

[Lukáš Tinkl]

Review: Needs Fixing

Unfortunately, this creates another regression, when using fullscreen apps:

1. start webbrowser
2. navigate to e.g. youtube.com and play a video
3. press the video's fullscreen button
4. open the window switcher (spread), select a different app
5. at this point, even without switching back, the webbrowser app is restored back to windowed state
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https://code.launchpad.net/~nick-dedekind/qtubuntu/1648842.window-focus-regression/+merge/312926
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