Fix the toggle button flicker problem when display

- Root cause: the side effect of the parallel controller loading.
- Solution: disable the parallel approach and remove the entry point
  of parallel approach in DashboardFragment.

Fixes: 187838753
Test: Robo test for AppInfoDashboardFragment, ConfigureNotificationSettings,
      ConnectedDeviceDashboardFragment, DevelopmentSettingsDashboardFragment,
      NetworkDashboardFragment, DashboardFragment
Change-Id: If3b09c4fd6f33042e0ed38704f08e855ab8f5377

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

@@ -95,11 +95,6 @@ public class NetworkDashboardFragment extends DashboardFragment implements
                 this /* fragment */, this /* mobilePlanHost */);
     }
 
-    @Override
-    protected boolean isParalleledControllers() {
-        return true;
-    }
-
     private static List<AbstractPreferenceController> buildPreferenceControllers(Context context,
             Lifecycle lifecycle, MetricsFeatureProvider metricsFeatureProvider, Fragment fragment,
             MobilePlanPreferenceHost mobilePlanHost) {