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 (!resolveSource.SetInternal(host)) {
                continue;
            }
            unsigned int nMaxIPs = 256; 
            if (LookupHost(host, vIPs, nMaxIPs, true)) {
                for (const CNetAddr& ip : vIPs) {
                    CAddress addr = CAddress(CService(ip, Params().GetDefaultPort()), requiredServiceBits);
                    addr.nTime = rng.rand_uniform_delay(Now<NodeSeconds>() - 3 * 24h, -4 * 24h); 
                    vAdd.push_back(addr);
                    found++;
                }
                addrman.Add(vAdd, resolveSource);
            } else {
                
                
                AddAddrFetch(seed);
            }
        }
        --seeds_right_now;
    }
    LogPrintf("%d addresses found from DNS seeds\n", found);
}
void CConnman::DumpAddresses()
{
    int64_t nStart = GetTimeMillis();
    DumpPeerAddresses(::gArgs, addrman);
    LogPrint(BCLog::NET, "Flushed %d addresses to peers.dat  %dms\n",
           addrman.size(), GetTimeMillis() - nStart);
}
void CConnman::ProcessAddrFetch()