Unwrap a Python 2.6 SSL socket, so we can call shutdown()

def _shutdown_transport(self):
        """
        Unwrap a Python 2.6 SSL socket, so we can call shutdown()

        """
        if HAVE_PY26_SSL and (self.sslobj is not None):
            self.sock = self.sslobj.unwrap()
            self.sslobj = None