b/3004029 Fixed content resolver loss

We were creating a static AsyncQueryHandler which only held a
weak reference to the content resolver. This caused db updates
to be dropped once the original context had been gc'd. This
fix creates a new handler for each update to ensure we have a
valid resolver.

Change-Id: I049d8390ac0215e12e63d57b0bae4d3f6df64b6a