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)
bilingual_str error;
        if (!NetWhitebindPermissions::TryParse(strBind, whitebind, error)) return InitError(error);
        connOptions.vWhiteBinds.push_back(whitebind);
    }
     If the user did not specify -bind= or -whitebind= then we bind
     on any a
    connOptions.bind_on_any = args.GetArgs("-bind").empty() && args.GetArgs("-whitebind").empty();
     Emit a warning if a bad port is given to -port= but only if -bind and -whitebind are not
     given, because if they are, then -port= is ignored.
    if (connOptions.bind_on_any && args.IsArgSet("-port")) {
        const uint16_t port_arg = args.GetIntArg("-port", 0);
        if (IsBadPort(port_arg)) {
            InitWarning(BadPortWarning("-port", port_arg));
        }
    }
    CService onion_service_target;
    if (!connOptions.onion_binds.empty()) {
        onion_service_target = connOptions.onion_binds.front();
    } else {
        onion_service_target = DefaultOnionServiceTarget();
        connOptions.onion_binds.push_back(onion_service_target);
    }
    if (args.GetBoolArg("-listenonion", DEFAULT_LISTEN_ONION)) {
        if (connOptions.onion_binds.size() > 1) {
            InitWarning(strprintf(_("More than one onion bind address is provided. Using %s "
                                    "for the automatically created Tor onion service."),
                                  onion_service_target.ToStringIPPort()));
        }
        StartTorControl(onion_service_target);
    }