fix security issue #36564 (integrity error w/ RQLUniqueConstraint) by using a global lock serializing commit when some RQLUniqueConstraint is encountered.
# server.__init__
"""
: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
"""