[PATCH] stream/tcp: don't reject on bad ack

[PATCH] stream/tcp: don't reject on bad ack

Not using a packet for the streaming analysis when a non zero
ACK value and ACK bit was unset was leading to evasion as it was
possible to start a session with a SYN packet with a non zero ACK
value to see the full TCP stream to escape all stream and application
layer detection.

This addresses CVE-2021-35063.

Fixes: fa692df37 ("stream: reject broken ACK packets")
Ticket: #4504.

Gbp-Pq: Name stream-no-reject-bad-ack.patch