### 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

},
            }.Check(request);
    
    
    pwallet->BlockUntilSyncedToCurrentChain();
    auto locked_chain = pwallet->chain().lock();
    LOCK(pwallet->cs_wallet);
    RPCTypeCheckArgument(request.params[0], UniValue::VBOOL);
    bool fUnlock = request.params[0].get_bool();
    if (request.params[1].isNull()) {
        if (fUnlock)
            pwallet->UnlockAllCoins();
        return true;
    }
    RPCTypeCheckArgument(request.params[1], UniValue::VARR);
    const UniValue& output_params = request.params[1];
    
    std::vector<COutPoint> outputs;
    outputs.reserve(output_params.size());
    for (unsigned int idx = 0; idx < output_params.size(); idx++) {
        const UniValue& o = output_params[idx].get_obj();
        RPCTypeCheckObj(o,
            {
                {"txid", UniValueType(UniValue::VSTR)},
                {"vout", UniValueType(UniValue::VNUM)},
            });
        const uint256 txid(ParseHashO(o, "txid"));
        const int nOutput = find_value(o, "vout").get_int();
        if (nOutput < 0) {
            throw JSONRPCError(RPC_INVALID_PARAMETER, "Invalid parameter, vout must be positive");