### 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

{"include_watchonly", RPCArg::Type::BOOL,  "true for watch-only wallets, otherwise false", "Include transactions to watch-only addresses (see 'importaddress')"},
                },
                RPCResult{
            "[\n"
            "  {\n"
            "    \"involvesWatchonly\": xxx, (bool) Only returns true if imported addresses were involved in transaction.\n"
            "    \"address\":\"address\",    (string) The bitcoin address of the transaction.\n"
            "    \"category\":               (string) The transaction category.\n"
            "                \"send\"                  Transactions sent.\n"
            "                \"receive\"               Non-coinbase transactions received.\n"
            "                \"generate\"              Coinbase transactions received with more than 100 confirmations.\n"
            "                \"immature\"              Coinbase transactions received with 100 or fewer confirmations.\n"
            "                \"orphan\"                Orphaned coinbase transactions received.\n"
            "    \"amount\": x.xxx,          (numeric) The amount in " + CURRENCY_UNIT + ". This is negative for the 'send' category, and is positive\n"
            "                                        for all other categories\n"
            "    \"label\": \"label\",       (string) A comment for the address/transaction, if any\n"
            "    \"vout\": n,                (numeric) the vout value\n"
            "    \"fee\": x.xxx,             (numeric) The amount of the fee in " + CURRENCY_UNIT + ". This is negative and only available for the \n"
            "                                         'send' category of transactions.\n"
            + TransactionDescriptionString()
            + "    \"abandoned\": xxx          (bool) 'true' if the transaction has been abandoned (inputs are respendable). Only available for the \n"
            "                                         'send' category of transactions.\n"
            "  }\n"
            "]\n"
                },
                RPCExamples{
            "\nList the most recent 10 transactions in the systems\n"
            + HelpExampleCli("listtransactions", "") +
            "\nList transactions 100 to 120\n"
            + HelpExampleCli("listtransactions", "\"*\" 20 100") +