[sobject] fix notification operation
regression introduced in bf4003760e02 Operation use self. session. not self._cw.
I'm a bit surprised that its not tested.
closes ##2870077
# -*- coding: utf-8 -*-
# copyright %(year)s %(author)s, all rights reserved.
# contact %(author-web-site)s -- mailto:%(author-email)s
#
%(long-license)s
"""%(distname)s schema"""