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)
.m_last_block_time = node->m_last_block_time,
                .m_last_tx_time = node->m_last_tx_time,
                .fRelevantServices = node->m_has_all_wanted_services,
                .m_relay_txs = node->m_relays_txs.load(),
                .fBloomFilter = node->m_bloom_filter_loaded.load(),
                .nKeyedNetGroup = node->nKeyedNetGroup,
                .prefer_evict = node->m_prefer_evict,
                .m_is_local = node->addr.IsLocal(),
                .m_network = node->ConnectedThroughNetwork(),
                .m_noban = node->HasPermission(NetPermissionFlags::NoBan),
                .m_conn_type = node->m_conn_type,
            };
            vEvictionCandidates.push_back(candidate);
        }
    }
    const std::optional<NodeId> node_id_to_evict = SelectNodeToEvict(std::move(vEvictionCandidates));
    if (!node_id_to_evict) {
        return false;
    }
    LOCK(m_nodes_mutex);
    for (CNode* pnode : m_nodes) {
        if (pnode->GetId() == *node_id_to_evict) {
            LogPrint(BCLog::NET, "selected %s connection for eviction peer=%d; disconnecting\n", pnode->ConnectionTypeAsString(), pnode->GetId());
            pnode->fDisconnect = true;
            return true;
        }
    }
    return false;
}
void CConnman::AcceptConnection(const ListenSocket& hListenSocket) {