torrc: use NodeConfig.hs_directory instead of hard-coding 'hidden_service'

    if n._config.hs:

        res += textwrap.dedent(

            f"""

            HiddenServiceDir {n.dir}/hidden_service

            HiddenServiceDir {n.dir.joinpath(n._config.hs_directory)}

            # Redirect requests to the port used by chutney verify

            HiddenServicePort {n.hs_virtport.unwrap()} 127.0.0.1:{n.hs_targetport.unwrap()}