Take MulticastLock on Android to ensure broadcast packets can be received (#9199)

* Take MulticastLock on Android to ensure broadcast packets can be received.  This may belong in Qt for Android.  See QTBUG-73138

* Use a more descriptive name for the WiFiManager Multicast Lock

android/AndroidManifest.xml

@@ -54,6 +54,9 @@
     <!-- Needed to keep working while 'asleep' -->
     <uses-permission android:name="android.permission.WAKE_LOCK"/>
 
+    <!-- Need MulticastLock to receive broadcast UDP packets  -->
+    <uses-permission android:name="android.permission.CHANGE_WIFI_MULTICAST_STATE"/>
+
     <!-- The following comment will be replaced upon deployment with default permissions based on the dependencies of the application.
          Remove the comment if you do not require these default permissions. -->
     <!-- %%INSERT_PERMISSIONS -->

android/src/org/mavlink/qgroundcontrol/QGCActivity.java

@@ -52,6 +52,7 @@ import android.hardware.usb.UsbManager;
 import android.widget.Toast;
 import android.util.Log;
 import android.os.PowerManager;
+import android.net.wifi.WifiManager;
 import android.os.Bundle;
 import android.app.PendingIntent;
 import android.view.WindowManager;
@@ -76,6 +77,7 @@ public class QGCActivity extends QtActivity
     private static PendingIntent                        _usbPermissionIntent = null;
     private TaiSync                                     taiSync = null;
     private Timer                                       probeAccessoriesTimer = null;
+    private static WifiManager.MulticastLock            _wifiMulticastLock;
     
     public static Context m_context;
 
@@ -222,6 +224,18 @@ public class QGCActivity extends QtActivity
         // Create intent for usb permission request
         _usbPermissionIntent = PendingIntent.getBroadcast(_instance, 0, new Intent(ACTION_USB_PERMISSION), 0);
 
+	// Workaround for QTBUG-73138
+	if (_wifiMulticastLock == null)
+            {
+                WifiManager wifi = (WifiManager) _instance.getSystemService(Context.WIFI_SERVICE);
+                _wifiMulticastLock = wifi.createMulticastLock("QGroundControl");
+                _wifiMulticastLock.setReferenceCounted(true);
+            }
+
+	_wifiMulticastLock.acquire();
+	Log.d(TAG, "Multicast lock: " + _wifiMulticastLock.toString());
+
+
         try {
             taiSync = new TaiSync();
 
@@ -259,6 +273,10 @@ public class QGCActivity extends QtActivity
         }
         unregisterReceiver(mOpenAccessoryReceiver);
         try {
+            if (_wifiMulticastLock != null) {
+                _wifiMulticastLock.release();
+                Log.d(TAG, "Multicast lock released.");
+            }
             if(_wakeLock != null) {
                 _wakeLock.release();
             }