fw/b: adb network tile: Don't make ConnectionManager get calls from callback

* We shouldn't be calling getLinkProperties() from inside the callback.

* Refactor to avoid this.  Code is also simpler as a result.

* Tested switching between wifi / mobile / vpn and adb tile still updates
  with the correct network address.

* Remove unused imports whilst we're here

Change-Id: I01416d4dcbb2f31bf7ba439385ad3caf186d1128