Skip refresh if number of pages hasn't changed

This gives a smoother animation when a media app is frequently
updating their notification.

Fixes: 157749719
Test: Play audio on SoundCloud with another media control appear in the
QS carousel. Page between players and check the animation of the page
indicator. It should be smooth and not jumpy.

Change-Id: Iabd77736eba0fb8e504297299a018079304c7489