Fix issue with animations that couldn't be started

If we can't create a remote animation target for some reason
(removed from task, no main window, etc), SurfaceAnimator
called startAnimation but we never invoke the finish callback.

Thus, we need to make sure to also invoke the finish callback
when not using the AppWindowToken as part of the remote animation.

This actually happens if the main intent clears the task, like
Settings. In that case, it removes all sub activities, which then
get added to mClosingApps, which then are part of a transition.

It's questionable why this would need to happen, but we don't have
the risk budget to go down that rabbit hole.

Test: RemoteAnimationControllerTest
Test: Open Settings -> Network -> Wifi, press home, reopen
Settings, repeat 10x
Test: adb shell dumpsys window -a
Fixes: 76438155
Change-Id: Ib528d5c0d3559eb20522799af68ebbfb17b9801b