IMS: Fix CF notification when enable through MMI code

Fix for the display of notification when CF enabled through
MMI code, override setVoiceCallForwardingFlag api in ImsPhone
which gets IccRecords from default phone object. To avoid
IccRecords being null when it gets from mIccRecords
in Phone object for ImsPhone.

Change-Id: I6c0887970d57ad4377270470e10517daed3de71d
CRs-Fixed: 1044029