Call finishedCallback if dream unocclude animation starts late

The onFinishedCallback isn't being called if the dream-to-X transition
finishes before the unocclude animation starts. Since we set
mUnoccludeFinishedCallback in onAnimationStart, and if that's called
after dreamViewModel.getTransitionEnded(), the callback is null.
Fix is in onAnimationStart, call onFinished if dream exit transition
is complete.

Also added some logging to help track down issue.

Fixes: 410801573
Test: atest KeyguardViewMediatorTestKt
Flag: EXEMPT bugfix
Change-Id: I16678b9809dd991dde37c2338a48267c174564fc