Do not set TaskFragment surface position if in change transition

When it is freezed in change transition, the animation handler should
handle the position change. After the animation leash is removed, the
TaskFragment position will be updated in #onAnimationLeashLost

Bug: 196173550
Test: test with demo app
Change-Id: I4048dbe8ae0db0354cd9bf0ef08bab9d897a65b0