fw/b: Allow adb over network when any default network is active

* Track the android default network instead of wifi state.

* If on, always allow toggle off regardless of whether the
  network disappears on you.

* When toggled on and network has gone show "no network"
  in place of the local link address.

Change-Id: Ib8ee1b5334ed7409319f79716047b438a7bface8