auth: added selector to support new ldap admin groups sync method.

rhodecode/templates/admin/auth/plugin_settings.mako

@@ -112,6 +112,7 b''
     $("#tls_reqcert").select2(select2Options);
     $("#search_scope").select2(select2Options);
     $("#group_extraction_type").select2(select2Options);
+    $("#admin_groups_sync").select2(select2Options);
 });
 </script>
 </%def>