[facets] should remove groupby from base rqlst. Closes #1796196 as we search for values for a variable, there seems to be no case where we would be interested in groups, though there are clearly some were leaving groups cause errors.

bgcolor = '#000000'
stylesheets = ['%s/cubicweb.css' % datadir_url]
logo = '%s/logo.png' % datadir_url
lazy = lazystr('%(bgcolor)s')