Fix the consistency of connection status displayed on Wi-Fi card

- Refresh slice in WifiTracker.onConnectedChanged
- Only expose notifySliceChange to child in SliceBackgroundWorker

Fixes: 123270015
Test: make RunSettingsRoboTests -j ROBOTEST_FILTER=com.android.settings.wifi.slice
Change-Id: Id5540ebae2746e58e14924665c5e62bf437ebcf0

src/com/android/settings/wifi/slice/WifiSlice.java

@@ -292,11 +292,12 @@ public class WifiSlice implements CustomSliceable {
 
         @Override
         public void onWifiStateChanged(int state) {
-            mContext.getContentResolver().notifyChange(getUri(), null);
+            notifySliceChange();
         }
 
         @Override
         public void onConnectedChanged() {
+            notifySliceChange();
         }
 
         @Override