Fix to exit ECBM when there is RAT change

When there is RAT change from CDMA to GSM send request to exit ECBM to
RIL and clean up the UI for ECBM before disposing CDMA phone object.

Change-Id: If5eac0d4d247ee88da4f602d5f3e0b1533fe7134
CRs-Fixed: 671156