Send finishTransaction for aborted transition

- If finishTransaction for an aborted transition is available send that
  instead of hardcoded null.
- This helps in correcting any custom layering in the transition
  handler.

Flag: EXEMPT (Bug fix)
Bug: 419652416
Bug: 385142011
Test: atest ShellTransitionTests
Test: Manually verified by starting an aborted transition and then doing
      setLayer via the finishTransaction that is received
Change-Id: Iad04b3b394366521a2918e2514cadf965057a8f4