Don't update the bubble on ranking changes if it's already in the stack

The only reason we should update/add a bubble in response to a ranking
change is if that notification wasn't a bubble before and should be
now.

Also set the entry when retrieving from pending / overflow.

Bug: 152322244
Test: manual - 1) add some bubbles, add one that auto expanded
               2) collapse stack
               3) trigger some notification in shade (e.g. start a timer)
               => notice the stack does not auto expand in the background
Change-Id: I15877fabf07a402dade76904dc1481ab669776ff