Two fixes on autofill save.

1.Fixed race condition on save request - if the service was unbound, it would
  mark the RemoteFillService as completed and the retry would be dropped.
2.Removed session when save request is canceled.

Change-Id: Ib71514cdcfecc38c07dd7656174d0db68ed758d1
Fixes: 36001206
Test: CtsAutoFillServiceTestCases pass