Fixing call notifications for FBE

+ The NotificationBroadcastReceiver needs to be encryption aware so
it runs and can be used to accept/decline calls when the device is
file based encryption locked.
+ Prior to this change, the buttons in call notifications wouldn't do
anything because the BroadcastReceiver didn't exist in this locked
state.

Bug: 27172859
Change-Id: Ib5e17f4c530820a42af97d2d2d9aae327273b9df