webui: preload automember default group select list

- the reload also fixes vertical align in Firefox (input gets
  display='inline' style).

Reviewed-By: Endi Sukma Dewata <edewata@redhat.com>

install/ui/src/freeipa/automember.js

@@ -688,6 +688,7 @@ IPA.automember.default_group_widget = function(spec) {
         that.group_select_node = $('<div/>', { 'class': 'automember-header-control' });
         that.group_select.create(that.group_select_node);
         that.group_select_node.appendTo(container);
+        that.group_select.update([]); // preload groups
     };
 
     that.get_title = function() {