### 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

{
    std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
    CWallet* const pwallet = wallet.get();
    if (!EnsureWalletIsAvailable(pwallet, request.fHelp)) {
        return NullUniValue;
    }
    RPCHelpMan{"sendmany",
                "\nSend multiple times. Amounts are double-precision floating point numbers." +
                    HelpRequiringPassphrase(pwallet) + "\n",
                {
                    {"dummy", RPCArg::Type::STR, RPCArg::Optional::NO, "Must be set to \"\" for backwards compatibility.", "\"\""},
                    {"amounts", RPCArg::Type::OBJ, RPCArg::Optional::NO, "A json object with addresses and amounts",
                        {
                            {"address", RPCArg::Type::AMOUNT, RPCArg::Optional::NO, "The bitcoin address is the key, the numeric amount (can be string) in " + CURRENCY_UNIT + " is the value"},
                        },
                    },
                    {"minconf", RPCArg::Type::NUM, RPCArg::Optional::OMITTED_NAMED_ARG, "Ignored dummy value"},
                    {"comment", RPCArg::Type::STR, RPCArg::Optional::OMITTED_NAMED_ARG, "A comment"},
                    {"subtractfeefrom", RPCArg::Type::ARR, RPCArg::Optional::OMITTED_NAMED_ARG, "A json array with addresses.\n"
            "                           The fee will be equally deducted from the amount of each selected address.\n"
            "                           Those recipients will receive less bitcoins than you enter in their corresponding amount field.\n"
            "                           If no addresses are specified here, the sender pays the fee.",
                        {
                            {"address", RPCArg::Type::STR, RPCArg::Optional::OMITTED, "Subtract fee from this address"},
                        },