[forms] avoid to create superfluous add_new_relation_link in create form
CubicWeb.require('ajax.js');functionremoveBookmark(beid){d=asyncRemoteExec('delete_bookmark',beid);d.addCallback(function(boxcontent){reloadComponent('bookmarks_box','','boxes','bookmarks_box');document.location.hash='#header';updateMessage(_("bookmark has been removed"));});}