Settings: Respect preference's visibility in VideoPreferenceController

* Since AbstractPreferenceController's displayPreference()
  sets the visibility based on isAvailable() we need to
  set mVideoPreference early and make getAvailabilityStatus()
  return UNSUPPORTED_ON_DEVICE if needed.

Test: manual, open battery manager
Change-Id: Ibf72971b49fa1162fb99f9fc61cbb54ba39a2dfa