Fix Overlapping notifications when the swiping out is canceled

Fix the overlapping notification when the Shade is opened, a
notification is being swiped out, and the swiping out animation gets
canceled. The TransientView is added during the animation process, but
is not cleaned upon animation cancellation currently.

Bug: 298304967
Bug: 281628358
Test: Manual, open the Shade, swipe out a notification can cancel the
animation, there shouldn't be any uncleared TransientViews.

Change-Id: I4e626440302206ad2c93d4ca7641730918a457f2