Active display: make sure mNotificaiton is set correctly

Change-Id: I4111ca843e340cca4d6dac4b2c2922ce3039e487
Active display: register/unregister recievers and listeners when enabled/disabled

Change-Id: Ic73e63da2c9634bc864ab1a1387eb9145eb0b5b0
Active display: Unify (un)registering callbacks and add proper checks.

Change-Id: Ie4c4660a54d2c60831f7a3bcc66b3a9ca1d035f2