[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
if not rql('CWConstraintType X WHERE X name "RQLUniqueConstraint"',
ask_confirm=False):
rql('INSERT CWConstraintType X: X name "RQLUniqueConstraint"',
ask_confirm=False)