### 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

HelpExampleCli("setwalletflag", "avoid_reuse")
                  + HelpExampleRpc("setwalletflag", "\"avoid_reuse\"")
                },
            }.Check(request);
    std::string flag_str = request.params[0].get_str();
    bool value = request.params[1].isNull() || request.params[1].get_bool();
    if (!WALLET_FLAG_MAP.count(flag_str)) {
        throw JSONRPCError(RPC_INVALID_PARAMETER, strprintf("Unknown wallet flag: %s", flag_str));
    }
    auto flag = WALLET_FLAG_MAP.at(flag_str);
    if (!(flag & MUTABLE_WALLET_FLAGS)) {
        throw JSONRPCError(RPC_INVALID_PARAMETER, strprintf("Wallet flag is immutable: %s", flag_str));
    }
    UniValue res(UniValue::VOBJ);
    if (pwallet->IsWalletFlagSet(flag) == value) {
        throw JSONRPCError(RPC_INVALID_PARAMETER, strprintf("Wallet flag is already set to %s: %s", value ? "true" : "false", flag_str));
    }
    res.pushKV("flag_name", flag_str);
    res.pushKV("flag_state", value);
    if (value) {
        pwallet->SetWalletFlag(flag);
    } else {
        pwallet->UnsetWalletFlag(flag);
    }
    if (flag && value && WALLET_FLAG_CAVEATS.count(flag)) {
        res.pushKV("warnings", WALLET_FLAG_CAVEATS.at(flag));
    }
    return res;
}
static UniValue createwallet(const JSONRPCRequest& request)