Handle TO_BACK in PiP onTransitionConsumed

When the PiP task gets removed when the screen is off, the TO_BACK
transition would be aborted and leaves an inconsistent state:

- Task is reset to full-screen mode with full-screen bounds in Core
- Shell does not touch the Task leash and stills it's in PiP mode

Fixing this by re-use the mMoveToBackTransition to reset the Shell
states when in onTransitionConsumed if the transition is aborted.

Flag: EXEMPT bugfix
Video: http://recall/-/aaaaaabFQoRHlzixHdtY/giwcYi06KeZL2R07uGwh7k
Bug: 373693542
Test: manual test with the test app
Change-Id: Ie019f80b7f8df35d415c1846f1b5d856245c4374