Settings: Only disable menu unlock options with custom keyguard

These buttons have a proper use case with the regular lock
screen, but are not applicable to our custom lockscreen.

Change-Id: Ic5af82bc1998a2960ba44d4235881d46e5081e5b
Signed-off-by: Roman Birg <roman@cyngn.com>
(cherry picked from commit 1c5f27fe3abfe0933a3fbe18eeff3238523c6b7d)

Conflicts:
	src/com/android/settings/cyanogenmod/LockscreenButtons.java