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)
return InitError(strprintf(_("Prune configured below the minimum of %d MiB.  Please use a higher number."), MIN_DISK_SPACE_FOR_BLOCK_FILES  1024  1024));
        }
        fPruneMode = true;
    }
    nConnectTimeout = args.GetIntArg("-timeout", DEFAULT_CONNECT_TIMEOUT);
    if (nConnectTimeout <= 0) {
        nConnectTimeout = DEFAULT_CONNECT_TIMEOUT;
    }
    peer_connect_timeout = args.GetIntArg("-peertimeout", DEFAULT_PEER_CONNECT_TIMEOUT);
    if (peer_connect_timeout <= 0) {
        return InitError(Untranslated("peertimeout must be a positive integer."));
    }
    
    
    if (args.IsArgSet("-blockmintxfee")) {
        if (!ParseMoney(args.GetArg("-blockmintxfee", ""))) {
            return InitError(AmountErrMsg("blockmintxfee", args.GetArg("-blockmintxfee", "")));
        }
    }
    nBytesPerSigOp = args.GetIntArg("-bytespersigop", nBytesPerSigOp);
    if (!g_wallet_init_interface.ParameterInteraction()) return false;
    
    SetMockTime(args.GetIntArg("-mocktime", 0)); 
    if (args.GetBoolArg("-peerbloomfilters", DEFAULT_PEERBLOOMFILTERS))
        nLocalServices = ServiceFlags(nLocalServices | NODE_BLOOM);
    if (args.GetIntArg("-rpcserialversion", DEFAULT_RPC_SERIALIZE_VERSION) < 0)
        return InitError(Untranslated("rpcserialversion must be non-negative."));
    if (args.GetIntArg("-rpcserialversion", DEFAULT_RPC_SERIALIZE_VERSION) > 1)
        return InitError(Untranslated("Unknown rpcserialversion requested."));
    nMaxTipAge = args.GetIntArg("-maxtipage", DEFAULT_MAX_TIP_AGE);