Enable ipv6 for actions running on docker containers

[romeroalx]

Short description

Fix for #12844. Adds configuration to enable IPv6 for actions running on docker containers: options: --sysctl net.ipv6.conf.all.disable_ipv6=0.

Checklist

I have:

• read the CONTRIBUTING.md document
• compiled this code
• tested this code
• included documentation (including possible behaviour changes)
• documented the code
• added or modified regression test(s)
• added or modified unit test(s)
• checked that this code was merged to master

[romeroalx]

Hi @omoerbeek, before merging this PR there is something I would like to check with you.

Before introducing GH actions running on containers, we skipped some regression tests for Recursor, specifically in file regression-tests.recursor-dnssec/test_EDNSPadding.py, test addingAllowedAlwaysSameTagTest(RecursorEDNSPaddingTest) by setting the environment variable SKIP_IPV6_TESTS. More details here

I have tested removing that environment variable, and it seems that the test passes:

...
testQueryWithPadding (test_EDNSPadding.PaddingAllowedAlwaysSameTagTest) ... ok
testQueryWithoutEDNS (test_EDNSPadding.PaddingAllowedAlwaysSameTagTest) ... ok
testQueryWithoutPadding (test_EDNSPadding.PaddingAllowedAlwaysSameTagTest) ... ok
...

Do you remember why we were skipping those tests? Maybe we could leave those tests enabled again.

[omoerbeek]

It looks like there were originally disabled since CircleCI (which we used then) did not support IPV6. See b2d3e2b
They should no longer be disabled.

[romeroalx]

Good! Then no additional changes are required :)

Thank you @omoerbeek