Add a check to avoid losing focus

There is a scene as following:

1. The current active window is editor for typing word . we name the active window A.
2. A background monitoring application is launched and show a noinput and nofocus window only for showing a special message, then the window is closed . we name the window B.

In this case , window A should not lose focus because window B has not focus property . So ,we should add a check in X11Client::focusOutEvent, the fouceOutEvent will return without any process if current client is active ,because no other client get focus . m_focuesOutTimer cannot deactive window A , otherwise,the focus really lose in system.