Remove the previous animation split tasks container when recreating

Bug: 197919703
Test: Invoke split and swipe up a couple times, ensure the sf dump
      doesn't show multiple lingering split containers layers
Change-Id: Iad8b9d9a0d75bdaaa2a7255a33208c2c0c3fc25b
Merged-In: Iad8b9d9a0d75bdaaa2a7255a33208c2c0c3fc25b