Fix callback issue for AVD on UI thread

We have created AnimatorSet from XML, but it is assigned to the AVD only when
we start the animation due to theme-ing operations.

Given listeners can be added to AVD at any time, we have to cache them if
AnimatorSet is not setup yet.

b/26979225

Change-Id: I94315892de83f93a0205efe5e70dca0cd0f0a8e3