window: Pass the grab timestamp when updating the resize grab

Since XChangeActivePointerGrab doesn't have a direct equivalent
in XI2, we need to make sure we don't re-grab with a newer
tiemstamp.

src/core/window.c

@@ -9866,15 +9866,12 @@ meta_window_update_keyboard_resize (MetaWindow *window,
 
   if (update_cursor)
     {
-      guint32 timestamp;
-      /* FIXME: Using CurrentTime is really bad mojo */
-      timestamp = CurrentTime;
       meta_display_set_grab_op_cursor (window->display,
                                        NULL,
                                        window->display->grab_op,
                                        TRUE,
                                        window->display->grab_xwindow,
-                                       timestamp);
+                                       window->display->grab_timestamp);
     }
 }