Fix surface got offsetted twice while entering split

Split surface might be offsetted twice by RemoteAnimationController and
StageCoordinator#onStageVisibilityChanged. This removes surface
positioning from onStageVisibilityChanged because the split surface
should have been offsetted already by remote animation.

Bug: 199377815
Test: atest WMShellUnitTests
Test: trigger split from recent shortcut, observed split surfces are
      placed properly.
Test: drag to split, observed split surfaces been placed correctly.
Test: shell cmd to split, observed split surfaces been placed correctly.
Change-Id: I2ae1223eec130fa849e2aaa6d2e73ec3c9a845f2