[web auth] fix authentication pb when anonymous are allowed, avoiding the first authentifier to return an anon connection while a following one may find correct authentication info. This make things simpler (eventually)
"""allways executed before all others in server migration
:organization: Logilab
:copyright: 2001-2010 LOGILAB S.A. (Paris, FRANCE), license is LGPL v2.
:contact: http://www.logilab.fr/ -- mailto:contact@logilab.fr
:license: GNU Lesser General Public License, v2.1 - http://www.gnu.org/licenses
"""