Force-finish pending cancellation of the recents animation when process dies

- If the recents animation is cancelled, then we need to continue the
  deferred cancel when the process dies to ensure that the animation
  is cleaned up correctly (just calling cancel will no-op if the
  animation was already canceled and waiting for cleanupScreenshot()).

  This call to continue the deferred cancel is a no-op if there is no
  deferred cleanup.

Bug: 192564669
Test: atest RecentsAnimationControllerTest
Test: Defer cleanupScreenshot() and kill launcher process after canceling
Change-Id: I500b12dff2b3263e9e1529b4c094e4a422762d66