[Logout Greeter] Properly fullscreen window and don't bypass WM

Authored by broulik on Mar 22 2017, 9:53 AM.

Description

[Logout Greeter] Properly fullscreen window and don't bypass WM

Otherwise the window isn't fullscreen as far as kwin is concerned and then fast blur code path isn't executed.

Differential Revision: https://phabricator.kde.org/D5115