Fix issue with leaking death recipients

- When invalidating an existing external interface, we also need to
  unregister any listeners to ensure that binder death recipients are
  unlinked.  Otherwise, a crash in the process for the old listener
  can cause the current listener to be unregistered.

Bug: 242377577
Test: atest WMShellUnitTests
Change-Id: Ibb77ac19e4ebc616b8977db70d6269e3b930848e