QS: Fix missing tiles

It was possible for the state to be updated in the background
but before the callback was actually registered and never propagate
to the UI.  Call the callback directly after it is added (from the
QS thread) to ensure that the current state gets sent out on tiles
being added.

Change-Id: Idd76dce5cbc9dc9c99f9b3dc13998751fd170582
Fixes: 29419435