Fix crash/flicker with taskbar when canceling drag and drop

The surfaceControl transaction is performed more than once so close
the transaction at the end of the animation.

Test: manual - start a drag from taskbar into split and then pull it
               back so that it doesn't complete
             => ensure taskbar doesn't flicker / no crash in logs
Bug: 228006271
Change-Id: I38c8efe310596bbbbf09f361c266a7fefc1b2eea