Framework support to improve bg check CTS tests.

(Finally) introduce a new ServiceConnection callback to
tell you when the binding has died.  This allows you to robustly
have a weak service monitoring, and also is an easy way to find
out about breakages due to app updates etc.

Also clean up some debug output.

Test: moved to own suite and ran them.

Change-Id: I526cc00816c384fa9eb1312b92406f38085cbff9