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
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