Revert 43d471b9ab and apply correct bugfix:

Before, all clients were reconfigured to just raise them, when focus should
be set. However, this generated lots of notify events, which in turn lead
to an endless loop of setting focus, reconfiguring, setting focus, …

src/handlers.c

@@ -110,11 +110,6 @@ int handle_enter_notify(void *ignored, xcb_connection_t *conn, xcb_enter_notify_
                 return 1;
         }
 
-        /* When in stacking, enter notifications on the parent are ignored. Focus will be changed via keyboard only. */
-        if (client->container->mode == MODE_STACK &&
-            client == table_get(byParent, event->event))
-                return 1;
-
         set_focus(conn, client);
 
         return 1;