Since a new vehicle begins joystick polling when it becomes active it makes sense

that it should also end joystick polling when it becomes inactive. Otherwise we
may have stray threads hangin around.

src/Vehicle/Vehicle.cc

@@ -1865,6 +1865,7 @@ void Vehicle::setActive(bool active)
 {
     if (_active != active) {
         _active = active;
+        _startJoystick(false);
         emit activeChanged(_active);
     }
 }