Bug fix for back arrow behavior.

If the back arrow is triggered more than once, there's a bug in the
animation property that will prevent the UI from resurfacing. This fix
re-initialize the animation property so that the switches between the
snackbar and bottom sheet back-arrow is in a consistent, refreshed
state.

Bug: 280517963
Test: manual
Change-Id: I7c215b39a964360b2cca99bd8be98130128fa85f