Prioritize real joystick over virtual joystick.

Added conditional statement to disable the virtualTabletJoystick output if a real joystick is connected and enabled. Without this, two different sets of values would be sent and would appear highly sporadic.

src/Vehicle/Vehicle.cc

@@ -1215,5 +1215,8 @@ void Vehicle::_remoteControlRSSIChanged(uint8_t rssi)
 
 void Vehicle::virtualTabletJoystickValue(double roll, double pitch, double yaw, double thrust)
 {
+    // The following if statement prevents the virtualTabletJoystick from sending values if the standard joystick is enabled
+    if ( !_joystickEnabled ) {
         _uas->setExternalControlSetpoint(roll, pitch, yaw, thrust, 0, JoystickModeRC);
     }
+}