Add cleanupCalls to call tracker.

For GsmCdmaCallTracker, this calls pollCallsWhenSafe().  By polling the
calls in the RIL, the GSMCdmaCallTracker will reconcile the calls it knows
about with what the RIL reports, removing stale calls.

Test: Manual
Bug: 63317180
Change-Id: I7ee8609c41376bf21c428d04aab7d76151200699