Added onCallInitiating

* Add onCallInitiating which occurs as the first event after a session
begins to be established.
* onCallInitiating clears mPendingMO and purposely does not trigger an
extra state change since the state should already be in Dialing
* Added checks that initiating is called before progressing and that
each of them are called only once

Bug: 161218980
Test: FrameworksTelephonyTests
Change-Id: I0f73dbe150d69d36c05f1dab7006572868a79ec1