SECURITY FIX: Actually restrict the access to the printer to localhost

Before, any machine in any network connected by any of the interfaces (as
listed by "ifconfig") could access to an IPP-over-USB printer on the assigned
port, allowing users on remote machines to print and to access the web
configuration interface of a IPP-over-USB printer in contrary to conventional
USB printers which are only accessible locally.
void tcp_conn_close(struct tcp_conn_t *conn)
{
	close(conn->sd);
	free(conn);
}

void tcp_conn_close(struct tcp_conn_t *conn)
{
	close(conn->sd);
	free(conn);
}
