Camera2: Prevent autofocus when video snapshot is in progress

During video recording if screen is tapped repeatedly, autofocus is
started while the snapshot is taken. This would either result in an
out of focus snapshot which would also disturb the focus in the recorded
video or crash the sensors that can't handle autofocus during snapshot.

Change-Id: If2763094f5ab7536e4409469276de54580e803c8
Merge branch 'cm-11.0' of https://github.com/CyanogenMod/android_packages_apps_Camera2 into kitkat