Remove unused parameter and innocuous bug.

1. Remove the forUpdate boolean since no controller was using it.
2. Stop returning a boolean from JobStore.add(). It was always returning
   false because the remove() method would remove the added JobStatus
   object, not anything similar to the object. Thankfully, we were
   removing old JobStatus objects via another codepath, so the bug never
   surfaced as an issue.

Bug: 141645789
Test: Android builds
Change-Id: I17c7a4a629f033c574e4fbd625211c0fc476fcc9