[effects/diminactive] Fix false-triggering of the out animation

Summary:
In some cases, the out transition is false-triggered because we don't
react to changes in the keep-above and the full screen state.

Test Plan:

• Set the keep-above state on a window;
• Click on the desktop;
• (the window didn't "flicker")

Reviewers: KWin, davidedmundson

Reviewed By: KWin, davidedmundson

Subscribers: davidedmundson, abetts, kwin

Tags: KWin

Differential Revision: https://phabricator.kde.org/D16270