Media - Handle cleanup of pending notification entries

It is possible for notifications to be canceled prior to inflation,
which means there will not be a callback when the notification is
removed. Utitlize the NotifCollectionListener to get this event.

Fixes: 166315453
Test: manual, using RCNs to generate a race condition as they
create/cancel notifications immediately

Change-Id: I56d3ab9ef46d86c8623f9bac9152e8a2b8341c01