Windows: Fix window geometry when transiting from fullscreen to maximized.

The workaround added for QTBUG-8361 also needs to trigger in the
restore-from-fullscreen logic, set flag accordingly.

Task-number: QTBUG-40254
Task-number: QTBUG-8361
Change-Id: I6d6c35bb7004c84c6b8feea05ad974c23ca205d2
Reviewed-by: Oliver Wolff <oliver.wolff@digia.com>