LockScreen: Fix crash when unlocking twice

This will keep track if the BroadCastReceiver is registered and
will unregister it only if so.

Change-Id: I040d710cf0927394f36b2e3da251ac5a988ce1d6
Signed-off-by: Dirk Rettschlag <dirk.rettschlag@gmail.com>

Conflicts:
	policy/src/com/android/internal/policy/impl/keyguard/KeyguardSelectorView.java
KeygaurdSelectorView: Unregister reciever in onPause

Also check if we already have a reciever instance before
creating a new instance

Patch Set 2: Refactor field reciever to mUnlockReciever
           : Add null check to Context#unregisterReciever
Patch Set 3: Add null check to Vibrator#vibrate(int);
Change-Id: Ie9b03b20da29d05a64293ef6b7931393c34796a2

Conflicts:
	policy/src/com/android/internal/policy/impl/keyguard/KeyguardSelectorView.java
Fix Lockscreen FC/reboot

PS2: register receiver in onResume()

Change-Id: If475f0750bbc408e727eb0d3cf532c936ad418e8
Signed-off-by: Gergely Szell (sethyx) <szell@hu.ibm.com>