Guarantee transitions always update occlude status

Previously if the dream transition animation was not played, because eg.
dream was already showing before Keyguard but a transition was still set,
Keyguard would not log that it needs to be occluded now.

onAnimationStart is wrapped and return value checked to have a fallback
in case onAnimationStart doesn' startAnAnimation.

Change-Id: I00dd31606ed08b67666a58f1b3e2f0f3b31fcaa6
Test: Currently manual - start dream and then lockNow(null)
Bug: 270414686
(cherry picked from commit on googleplex-android-review.googlesource.com host: 7da8adaf)
Merged-In: I00dd31606ed08b67666a58f1b3e2f0f3b31fcaa6