### 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

{"sighashtype", RPCArg::Type::STR,  "ALL", "The signature hash type. Must be one of\n"
            "       \"ALL\"\n"
            "       \"NONE\"\n"
            "       \"SINGLE\"\n"
            "       \"ALL|ANYONECANPAY\"\n"
            "       \"NONE|ANYONECANPAY\"\n"
            "       \"SINGLE|ANYONECANPAY\""},
                },
                RPCResult{
            "{\n"
            "  \"hex\" : \"value\",                  (string) The hex-encoded raw transaction with signature(s)\n"
            "  \"complete\" : true|false,          (boolean) If the transaction has a complete set of signatures\n"
            "  \"errors\" : [                      (json array of objects) Script verification errors (if there are any)\n"
            "    {\n"
            "      \"txid\" : \"hash\",              (string) The hash of the referenced, previous transaction\n"
            "      \"vout\" : n,                   (numeric) The index of the output to spent and used as input\n"
            "      \"scriptSig\" : \"hex\",          (string) The hex-encoded signature script\n"
            "      \"sequence\" : n,               (numeric) Script sequence number\n"
            "      \"error\" : \"text\"              (string) Verification or signing error related to the input\n"
            "    }\n"
            "    ,...\n"
            "  ]\n"
            "}\n"
                },
                RPCExamples{
                    HelpExampleCli("signrawtransactionwithwallet", "\"myhex\"")
            + HelpExampleRpc("signrawtransactionwithwallet", "\"myhex\"")
                },
            }.Check(request);
    RPCTypeCheck(request.params, {UniValue::VSTR, UniValue::VARR, UniValue::VSTR}, true);