Fixing issue with flash during overview transition.

- This is due to the TransitionDrawable which does not actually
  start an animation until it is first drawn.  This workaround
  will just immediately reset the transition if it is not currently
  visible instead of animating (which is actually deferred until
  the next animation into overview mode).

Bug: 22414257
Change-Id: Id481303d0c99a20c1d16396c024ab50303f45576