Clean up onAnimationEnd handling

Unfortunately, this doesn't fix the issue. It does help with code
health, however. This change is based on the change made to the
wallpaper picker's version of the QS PageIndicator in ag/5872070.

Bug: 152093000
Test: manual - check page indicator for both QS tiles and media controls with >3 pages.
Change-Id: I23e6b5a03ab06f167407baffb4dc77f51b58926f