TempestaFW sometimes doesn't create IPv6 connections to servers.

[RomanBelozerov]

Describe the issue
TempestaFW sometimes doesn't create IPv6 connections to servers.

Expected Behavior
TempestaFW always create IPv6 connections to servers.

To Reproduce
Just run IPv6 tests on CI VMs without ping command before the tests. t_ipv6 from tempesta-test

Version or commit hash
kernel-version - 5.10.35.tfw-39c65d3
tempesta - 7833fa7
tempesta-test - c8c9ab6e3467e0f98b2e1e2b4c9c7e40fd13395e

Stacktrace or debug log
dmesg with DEBUG=1

[  170.580580] [tempesta fw]   start server: [2001:db8:1::115]:8000
[  170.581161] [tempesta fw]   start server: 192.168.122.4:8000
[  170.581695] [tempesta fw] Open listen socket on: [2001:db8:1::161]:443
[  170.582299] [tempesta fw]   start listening on socket: sk=000000009f13b602
[  170.582931] [tempesta fw] Open listen socket on: 192.168.122.9:443
[  170.583607] [tempesta fw]   start listening on socket: sk=000000002ebfe250
[  170.587356] [tempesta fw]   connected: 192.168.122.4:8000
[  170.589095] [tempesta fw]   connected: 192.168.122.4:8000

I there are no attempts to create a connection in tcpdump - t_ipv6.test_ipv6.TestIPv6Https.test_ipv6_to_ipv6.zip - not TCP SYN for IPv6, only for IPv4

I cannot reproduce this problem on my VMs

[EvgeniiMekhanik]

Closed by #2531