Improve chopper ack/retransmit reliability

It has been reported that Stegotorus can not reliably surf the web and it's most likely a problem with ack/retransmit feature.

One known problem is that in presence of ACKs, ST needs to wait until it has sent and received ACK(FIN) before closing a circuit, not until it has sent and received FIN.

The problem with this bug is that it can not be reproduced reliably but the bad proxy would hopefully solve this issue.

To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information