### 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{"getwalletinfo",
                "Returns an object containing various wallet state info.\n",
                {},
                RPCResult{
            "{\n"
            "  \"walletname\": xxxxx,               (string) the wallet name\n"
            "  \"walletversion\": xxxxx,            (numeric) the wallet version\n"
            "  \"balance\": xxxxxxx,                (numeric) DEPRECATED. Identical to getbalances().mine.trusted\n"
            "  \"unconfirmed_balance\": xxx,        (numeric) DEPRECATED. Identical to getbalances().mine.untrusted_pending\n"
            "  \"immature_balance\": xxxxxx,        (numeric) DEPRECATED. Identical to getbalances().mine.immature\n"
            "  \"txcount\": xxxxxxx,                (numeric) the total number of transactions in the wallet\n"