List the Ironic nodes UUID.

def list_nodes(self):
        """List the Ironic nodes UUID."""
        self.add_environment_file(user='stack', filename='stackrc')
        ret, _ = self.run("ironic node-list --fields uuid|awk '/-.*-/ {print $2}'", user='stack')
        # NOTE(Gonéri): the good new is, the order of the nodes is preserved and follow the one from
        # the instackenv.json, BUT it may be interesting to add a check.
        return ret.split()