Using Bitcoin Core v0.15.1

I have just set `onlynet=onion` in my `bitcoin.conf` file and have the following in my logs after node restart:

    2018-02-03 12:40:52 receive version message: /Satoshi:0.15.1/: version 70015, blocks=507429, us={IPv4}:{port), peer=0
    2018-02-03 12:41:15 receive version message: /Satoshi:0.14.2/: version 70015, blocks=507429, us={IPv4}:{port), peer=2
    2018-02-03 12:41:22 receive version message: /Satoshi:0.14.2/: version 70015, blocks=507429, us={IPv4}:{port), peer=3
    2018-02-03 12:41:28 receive version message: /Satoshi:0.15.0/: version 70015, blocks=507429, us={IPv4}:{port), peer=4
    2018-02-03 12:41:57 receive version message: /Satoshi:0.15.99/: version 70015, blocks=526679, us={IPv4}:{port), peer=5
    ...
    2018-02-03 12:44:11 receive version message: /Satoshi:0.15.1/: version 70015, blocks=507429, us=[::]:0, peer=6

The peer 6 was an onion.

My `bitcoin.conf` file is as follows:

    uacomment={redacted}
    prune=10239
    banscore=10
    bantime=31536000
    maxmempool=900
    mempoolexpiry=2160
    proxy=127.0.0.1:9050
    listen=1
    bind=127.0.0.1
    onlynet=onion

All the `Used for reaching peers via` tick boxes are still ticked but disabled when I look in Options>Newtork.

Bitcoin Core should not initiate IPv4 (or IPv6) connections when `onlynet=onion`.  These connections should not be seed nodes due to low addresses:

    2018-02-03 12:40:30 Loaded 66198 addresses from peers.dat  254ms

I get some IPv4 version messages each time I restart the node.

Note: added both `dns=0` and `dnsseed=0` at the same time and this *seems* to resolve the issue with limited testing. These entries should not be necessary to limit IPv4 outgoing connect.

If people need to setup Tor for testing, the setup I have used is here on [Bitcoin.SE](https://bitcoin.stackexchange.com/a/70070/75001)
}
        if (tip_info && chainman.m_best_header) {
            tip_info->header_height = chainman.m_best_header->nHeight;
            tip_info->header_time = chainman.m_best_header->GetBlockTime();
        }
    }
    LogPrintf("nBestHeight = %d\n", chain_active_height);
    if (node.peerman) node.peerman->SetBestHeight(chain_active_height);
     Map ports with UPnP or NAT-PMP.
    StartMapPort(args.GetBoolArg("-upnp", DEFAULT_UPNP), gArgs.GetBoolArg("-natpmp", DEFAULT_NATPMP));
    CConnman::Options connOptions;
    connOptions.nLocalServices = nLocalServices;
    connOptions.nMaxConnections = nMaxConnections;
    connOptions.m_max_outbound_full_relay = std::min(MAX_OUTBOUND_FULL_RELAY_CONNECTIONS, connOptions.nMaxConnections);
    connOptions.m_max_outbound_block_relay = std::min(MAX_BLOCK_RELAY_ONLY_CONNECTIONS, connOptions.nMaxConnections-connOptions.m_max_outbound_full_relay);
    connOptions.nMaxAddnode = MAX_ADDNODE_CONNECTIONS;
    connOptions.nMaxFeeler = MAX_FEELER_CONNECTIONS;
    connOptions.uiInterface = &uiInterface;
    connOptions.m_banman = node.banman.get();
    connOptions.m_msgproc = node.peerman.get();
    connOptions.nSendBufferMaxSize = 1000 * args.GetIntArg("-maxsendbuffer", DEFAULT_MAXSENDBUFFER);
    connOptions.nReceiveFloodSize = 1000 * args.GetIntArg("-maxreceivebuffer", DEFAULT_MAXRECEIVEBUFFER);
    connOptions.m_added_nodes = args.GetArgs("-addnode");
    connOptions.nMaxOutboundLimit = *opt_max_upload;
    connOptions.m_peer_connect_timeout = peer_connect_timeout;
     Port to bind to if `-bind=addr` is provided without a `:port` suffix.
    const uint16_t default_bind_port =
        static_cast<uint16_t>(args.GetIntArg("-port", Params().GetDefaultPort()));
    const auto BadPortWarning = [](const char* prefix, uint16_t port) {
        return strprintf(_("%s request to listen on port %u. This port is considered \"bad\" and "