QuickSettings : Properly restore lockscreen tile state

The keyguard lock relies on device policy manager service to be active,
currently it fails because it tries to request before its up. Fix that
by registering the request in a receiver

Change-Id: I15e0d980ecf21c8316f4a771e93f4b520c556115

Conflicts:
	packages/SystemUI/src/com/android/systemui/quicksettings/ToggleLockscreenTile.java
QuickSettings : Register/unregister cast tile one time

Don't do these operations every time the parent is visible/invisible,
it causes jank.

Repro:

Turn on wifi on a network w/ chromecast
Swipe down quick settings panel really fast

Change-Id: I3dfcd3610abe96e1bfdab06ef3b876ccf5140ceb