android: fix network change handling on API levels < 24

Author: dmytroreutov

android/src/main/java/io/grpc/android/AndroidChannelBuilder.java

@@ -323,17 +323,15 @@ public void onBlockedStatusChanged(Network network, boolean blocked) {
 
     /** Respond to network changes. Only used on API levels < 24. */
     private class NetworkReceiver extends BroadcastReceiver {
-      private boolean isConnected = false;
 
       @SuppressWarnings("deprecation")
       @Override
       public void onReceive(Context context, Intent intent) {
         ConnectivityManager conn =
             (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
         android.net.NetworkInfo networkInfo = conn.getActiveNetworkInfo();
-        boolean wasConnected = isConnected;
-        isConnected = networkInfo != null && networkInfo.isConnected();
-        if (isConnected && !wasConnected) {
+        boolean isConnected = networkInfo != null && networkInfo.isConnected();
+        if (isConnected) {
           delegate.enterIdle();
         }
       }