IMS:silent redial/srvcc call cleanup.

When silent redial or srvcc occurs. the IMSPhone call state is not set to idle
even after the call is ended. Also, the mConnection in mHandoverCall is not
cleaned up. This CL is to fix these 2 issues.

Bug:  19035679
Change-Id: I6bee704e2d7d8bf05ca1a910d25af4a02347328b