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 (connOptions.bind_on_any) {
         Only 
         any a
        Discover();
    }
    for (const auto& net : args.GetArgs("-whitelist")) {
        NetWhitelistPermissions subnet;
        bilingual_str error;
        if (!NetWhitelistPermissions::TryParse(net, subnet, error)) return InitError(error);
        connOptions.vWhitelistedRange.push_back(subnet);
    }
    connOptions.vSeedNodes = args.GetArgs("-seednode");
     Initiate outbound connections unless connect=0
    connOptions.m_use_addrman_outgoing = !args.IsArgSet("-connect");
    if (!connOptions.m_use_addrman_outgoing) {
        const auto connect = args.GetArgs("-connect");
        if (connect.size() != 1 || connect[0] != "0") {
            connOptions.m_specified_outgoing = connect;
        }
    }
    const std::string& i2psam_arg = args.GetArg("-i2psam", "");
    if (!i2psam_arg.empty()) {
        CService addr;
        if (!Lookup(i2psam_arg, addr, 7656, fNameLookup) || !addr.IsValid()) {
            return InitError(strprintf(_("Invalid -i2psam address or hostname: '%s'"), i2psam_arg));
        }
        SetProxy(NET_I2P, Proxy{addr});
    } else {
        SetReachable(NET_I2P, false);
    }