Skip default animation of embedded activity for scene transition

If the app specifies makeSceneTransitionAnimation. The animation
should be handled by itself.

Bug: 283213473
Test: On device which supports embedded activity:
      Open Settings, search, click back arrow to leave search.
      It should run a fade animation by ExitTransitionCoordinator
      instead of with an additional slide animation.
Change-Id: Ie056da5711c4bc04bf5ccfd1fe12c181daa956c2