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