xfreerdp-server: Fixed deadlock issue in event queue.

Writing to the pipe may block if the pipe is full. Holding the mutex while writing prevents listeners from
aquiring the mutex and unblocking the write. This leads to a deadlock situation.

server/X11/xf_event.c

@@ -96,9 +96,9 @@ void xf_event_push(xfEventQueue* event_queue, xfEvent* event)
 
 	event_queue->events[(event_queue->count)++] = event;
 
-	xf_set_event(event_queue);
-
 	pthread_mutex_unlock(&(event_queue->mutex));
+
+	xf_set_event(event_queue);
 }
 
 xfEvent* xf_event_peek(xfEventQueue* event_queue)