Fixed some notification leaks

Since we're now allowing heads-up on the lockscreen
the addedHeadsUpChildren list would fill up, even
if animations were not enabled.

This also fixes that the ExpandHelper and the DragDownHelper
would not realease the view on up.

Change-Id: I8c1b54ff4b034a8f4f2219534a707bbd792b8efa
Fixes: 35375214