“Registered server transport ...” should not be a warning

From register_server_proxy in src/or/transports.c:

    /* LOG_WARN so that the bridge operator can easily find the
       transport's port in the log file and send it to the users. */
    log_warn(LD_GENERAL, "Registered server transport '%s' at '%s:%d'",
             t->name, fmt_addr(&t->addr), (int)t->port);