Settings: Privacy Guard: Fix missing background tab

 * Changes introduced in Android 7.0 added a new UI
    to control the apps running in background,
    adding our tabs created an offset of 1 that breaks
    the bootup and superuser list content links

 * Add the invisible tab to its categories location
    and allow the CM tabs to be listed properly

 * Reference: f467c0ac

Change-Id: Iacecc532592490e708b97189f28fba79b09b7235