Record number of calls to FalsingManager before success/failure.

Track this number for metrics and success evaluation. Ideally,
the number of calls to the FalsingManager before the phone unlocks
should be 1. Driving this number closer to one should be a
"North Star" metric for falsing.

Bug: 130256776
Test: Manual
Change-Id: If8678b56e8d5301b595de32945a14f2df9589c61