ImsPhone: defer intial roaming state update

        updateDataServiceState();

        mDefaultPhone.registerForServiceStateChanged(this, EVENT_SERVICE_STATE_CHANGED, null);

        // Force update roaming state

        updateRoamingState(getCurrentRoaming());

        // Force initial roaming state update later, on EVENT_CARRIER_CONFIG_CHANGED.

        // Settings provider or CarrierConfig may not be loaded now.

    }

    //todo: get rid of this function. It is not needed since parentPhone obj never changes