Don't let apps disable the SIM PIN entry screen.

As the user (who controls the app behaviour after all) likely doesn't
see the PIN screen as a lock screen (he likely wants telephony) and the
PIN screen is not shown on a timer-driven basis, it should be treated
specially.

Change-Id: I8d48ab5f097bc926f67eab5835d9b5f1e581db15

Conflicts:
	packages/Keyguard/src/com/android/keyguard/KeyguardViewMediator.java