Ensure we call cancel in a few more fallback cases

- We should always cancel and notify the listener after the recents
  transition is started.  These are mainly edge cases where transition
  handling goes wrong or Launcher erroneously starts a recents
  transition while on the homescreen.

Bug: 329324086
Test: atest WMShellUnitTests
Change-Id: I36c61d9efd3157a84f31e969a9f10a13c3e77eb3