ViewPropertyAnimator cancels prior animations

The initial approach of VPA was to cancel previous animations
on the same exact set of properties. This worked in most cases,
but if the new animation had a different set of properties
(like animating alpha, x, and y instead of just x and y), then
there was a possible artifact as the old animation continued to
run in the background and could show the button in the wrong
location as a result.

The new approach is to search all running animations for
a property when a new animation is requested on it and to
remove that property from the list of properties being animated
by that previous animation. The prior animations continue to
run, but will no longer update that property, which will now be
controlled solely by the new animation requested.

Change-Id: Ib35d54a5e91be0a1310725be6e2acbaa6ead4a4e