Use RemoteCall for quota exceeded in backups

For both key-value and full-backup. This makes the tasks wait for the
quota exceeded call, allowing the agent to complete before being torn
down (as described in bug). Also added a short time-out (3s) in case of
misbehaving agents.

Bug: 68762178
Bug: 110082831
Test: atest FrameworksServicesRoboTests
Test: 1. while true; do atest FullBackupQuotaTest; done
      2. Stop after ~50 executions, verify all succeeded.
Test: 1. while true; do atest KeyValueQuotaTest; done
      2. Stop after ~50 executions, verify all succeeded.
Test: CtsBackupTestCases

Change-Id: Ib582e75a4d317ab53a6df8cb261966a04ef085fb