Make sure that celltoolbars are hidden

when a notebook without "celltoolbar" entry in metadata is loaded.

IPython/html/static/notebook/js/notebook.js

@@ -2103,6 +2103,8 b' var IPython = (function (IPython) {'
         if (this.metadata.celltoolbar) {
             IPython.CellToolbar.global_show();
             IPython.CellToolbar.activate_preset(this.metadata.celltoolbar);
+        } else {
+            IPython.CellToolbar.global_hide();
         }
 
         // now that we're fully loaded, it is safe to restore save functionality