Settings: Dissallow privacy guarding system apps on overlay.

  Bandaid fix for google play services inundating the permission
  dialog request queue within AppOps service and causing watchdog
  to consistently kill the system server's activity manager service
  which is deadlocked retrieving dialogs from the queue.

Change-Id: I10c432cebe6a4199517839598046eee7d19dcf72
TICKET: CYNGNOS-2869
(cherry picked from commit be7d45fd)