Fix WiFi show "Not connected" always issue

- The WiFi summary is designed to be changed when the
onCapabilitiesChanged() callback is made from the ConnectivityManager,
but there is no guarantee that there will be a callback after the
settings are registered to the ConnectivityManager.

- Need to fatch initial state information to show the correct summary
first when the settings register callback to the ConnectivityManager.

- Screenshot:
  https://screenshot.googleplex.com/AwmLX2ZQE2grC7N

Bug: 179335681
Test: manual test
- make RunSettingsRoboTests ROBOTEST_FILTER=WifiSummaryUpdaterTest

Change-Id: Ib5d22bdf34a3832dd5082e6e11cee699694afdee

src/com/android/settings/wifi/WifiSummaryUpdater.java

@@ -74,6 +74,7 @@ public final class WifiSummaryUpdater extends SummaryUpdater {
     @Override
     public void register(boolean register) {
         if (register) {
+            mWifiTracker.fetchInitialState();
             notifyChangeIfNeeded();
             mContext.registerReceiver(mReceiver, INTENT_FILTER);
         } else {