Settings: remove preference if device hasn't LockClock installed

Change-Id: I8b43501af12a3f4eba3a4ee87dbd416662639886
Merge "Settings: remove preference if device hasn't LockClock installed" into cm-11.0
Merge branch 'cm-11.0' of git://github.com/CyanogenMod/android_packages_apps_Settings into cm-11.0