Cleanup CallManager code.

Removed some methods which are not used in callmanager.  Ultimately the
entire class will be removed in the future.  For now baby steps.
Removed unused dependency on CallManager in SubscriptionController.

Test: Ran tests, compiled.
Bug: 115776310
Change-Id: I4c781b1d0ece48bafd5dbd68bd61ebef439580e2