Ensure that we consume the original mixed transition when handling keyguard

- Prior to calling onTransitionConsumed, we add another mixed keyguard
  transition handler to the list with the same transition, and
  onTransitionConsumed iterates the active transitions backwards and
  finds the newly added MixedTransition instead of the original

Bug: 329324086
Bug: 339038054
Test: Artificially fall into the keyguard path and verify it was finding
      the wrong mixed transition
Change-Id: I654b4b89448a9e15000c3e34103cf6f0359be02b