Allow us back on the network after carrier-detatch

We had code in DcTracker to deal with this but the MR1-originating
DcSwitchStateMachine interceeds.  Exposing the switch so
DSSM can access it and behave appropriately.

bug:23069223
Change-Id: I7a674d3b662aa0a7eec5a54889a784a2b64d662c