Update summary for AllInOneTetherPreference accordingly

The summary for AllInOneTetherPreference in NetworkDashboardFragment is
updated according to tethering state and tether interface chosen by
user.

Bug: 149256198
Test: AllInOneTetherPreferenceControllerTest, TetherEnablerTest,
CodeInspectionTest

Change-Id: I24ba4deabbb02b203e76d32048040d7ccf1b2d22

src/com/android/settings/network/NetworkDashboardFragment.java

@@ -66,7 +66,7 @@ public class NetworkDashboardFragment extends DashboardFragment implements
 
         use(MultiNetworkHeaderController.class).init(getSettingsLifecycle());
         use(AirplaneModePreferenceController.class).setFragment(this);
-        use(AllInOneTetherPreferenceController.class).init(getSettingsLifecycle());
+        getSettingsLifecycle().addObserver(use(AllInOneTetherPreferenceController.class));
     }
 
     @Override