Fix status bar app name/icon overlap

This issue was caused by a missing check for if there is a
waiting entry for the given key in BaseHeadsUpManager.removeEntry

Also add more stack call tracing to HeadsUpManagerLogger to
improve debugging

Fixes: 340334234
Test: manual with test app:
      send default notifs to get notif icons in status bar
      tap add 3 times fast
      during the initial appear animation, tap cancel all
      => see that app name is replaced by app icons
Change-Id: I5d7a59e83cf98d96297d40750ed7d8243b098709