add PhoneStateListener in DcController which fires at carrierNetworkChange event.

when DataConnection exits, it checks the mExecutingCarrierChange variable in
DcController. if it's under ExecutingCarrierChange, it updates the
reason field of networkInfo as carrierChange.

Bug: b/21706784
Change-Id: Ic9e7daf3bbc48db3cbe7be5ce1e2606f759d5edf