Reset HUN roundness after cancellation of disappearing animation

If the disappear animation of a notification is canceled before it
finishes, the roundness of the notification may remain in an
inconsistent state. After a debug session, it was determined that the
simplest solution was to handle the animation cancellation rather than
prevent it.

Test: atest ExpandableNotificationRowTest
Bug: 289805597
Change-Id: Ie88e1cbe2f562a7d818ae051d5cb67c4c856be8b