### Describe the issue

Testing in bitcoin 0.13.0, calling `bitcoin-cli listsinceblock x` is outputting all double-spent transactions that are in the wallet, even those that were double-spent well and truly before x.
### Is the issue reproducible?

Yes
#### List steps to reproduce below:
1.   Create a double-spend send to your wallet (easiest using bip125)
2.   Wait until one confirms, and then wait a few more blocks
3.   Run `bitcoin-cli listsinceblock $(bitcoin-cli getbestblockhash)` and it will output the double spent transaction
### Expected behavior

The double-spent transaction that was conflicted before the block hash should be filtered

const CTxDestination& address = item_it->first;
        const std::string& label = item_it->second.name;
        auto it = mapTally.find(address);
        if (it == mapTally.end() && !fIncludeEmpty)
            continue;
        CAmount nAmount = 0;
        int nConf = std::numeric_limits<int>::max();
        bool fIsWatchonly = false;
        if (it != mapTally.end())
        {
            nAmount = (*it).second.nAmount;
            nConf = (*it).second.nConf;
            fIsWatchonly = (*it).second.fIsWatchonly;
        }
        if (by_label)
        {
            tallyitem& _item = label_tally[label];
            _item.nAmount += nAmount;
            _item.nConf = std::min(_item.nConf, nConf);
            _item.fIsWatchonly = fIsWatchonly;
        }
        else
        {
            UniValue obj(UniValue::VOBJ);
            if(fIsWatchonly)
                obj.pushKV("involvesWatchonly", true);
            obj.pushKV("address",       EncodeDestination(address));
            obj.pushKV("amount",        ValueFromAmount(nAmount));
            obj.pushKV("confirmations", (nConf == std::numeric_limits<int>::max() ? 0 : nConf));
            obj.pushKV("label", label);