### 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

"\nAs a JSON-RPC call\n"
            + HelpExampleRpc("listtransactions", "\"*\", 20, 100")
                },
            }.Check(request);
    
    
    pwallet->BlockUntilSyncedToCurrentChain();
    const std::string* filter_label = nullptr;
    if (!request.params[0].isNull() && request.params[0].get_str() != "*") {
        filter_label = &request.params[0].get_str();
        if (filter_label->empty()) {
            throw JSONRPCError(RPC_INVALID_PARAMETER, "Label argument must be a valid label name or \"*\".");
        }
    }
    int nCount = 10;
    if (!request.params[1].isNull())
        nCount = request.params[1].get_int();
    int nFrom = 0;
    if (!request.params[2].isNull())
        nFrom = request.params[2].get_int();
    isminefilter filter = ISMINE_SPENDABLE;
    if (ParseIncludeWatchonly(request.params[3], *pwallet)) {
        filter |= ISMINE_WATCH_ONLY;
    }
    if (nCount < 0)
        throw JSONRPCError(RPC_INVALID_PARAMETER, "Negative count");
    if (nFrom < 0)
        throw JSONRPCError(RPC_INVALID_PARAMETER, "Negative from");
    UniValue ret(UniValue::VARR);
    {