[wayland] Dispatch the WaylandServer once more before killing internal client

This is needed to not deadlock during tear down in case the client wants
to dispatch events and the server is in wait for client.

wayland_server.cpp

@@ -70,6 +70,7 @@ WaylandServer::WaylandServer(QObject *parent)
 WaylandServer::~WaylandServer()
 {
     if (m_internalConnection.client) {
+        dispatch();
         m_internalConnection.client->deleteLater();
         m_internalConnection.clientThread->quit();
         m_internalConnection.clientThread->wait();