Dismiss systemui QS dialogs on screen off.

CLOSE_SYSTEM_DIALOGS may not be sent if the user turns off and on the
screen quickly, resulting in systemui dialogs being displayed over the
lock screen. Dismissing these system dialogs when the SCREEN_OFF
broadcast is sent prevents this bug.

Change-Id: I097d0997d1538002b23bdd8f7aa32ecf4d32e0d4
Fixes: 78915648
Test: manual