### 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

{
            RPCHelpMan{"unloadwallet",
                "Unloads the wallet referenced by the request endpoint otherwise unloads the wallet specified in the argument.\n"
                "Specifying the wallet name on a wallet endpoint is invalid.",
                {
                    {"wallet_name", RPCArg::Type::STR,  "the wallet name from the RPC request", "The name of the wallet to unload."},
                },
                RPCResults{},
                RPCExamples{
                    HelpExampleCli("unloadwallet", "wallet_name")
            + HelpExampleRpc("unloadwallet", "wallet_name")
                },
            }.Check(request);
    std::string wallet_name;
    if (GetWalletNameFromJSONRPCRequest(request, wallet_name)) {
        if (!request.params[0].isNull()) {
            throw JSONRPCError(RPC_INVALID_PARAMETER, "Cannot unload the requested wallet");
        }
    } else {