fix cgroupsv1 support in warden

[mkocher]

The new error checking was finding errors. Going back to the old code which did not check for errors but did work for teams. Jammy-on-Jammy -on-Garden is a pretty niche use case these days, so this seems ok.

Fixes #562

[coderabbitai]

Walkthrough

The changes refactor cgroup type detection in monit access helpers. A new helper function monit_using_unified_cgroup_v2() was added to detect cgroup v2 by checking for /sys/fs/cgroup/cgroup.controllers or validating the filesystem type of /sys/fs/cgroup. The detection logic in permit_monit_access() was updated to use this helper instead of grepping /proc/self/cgroup. Additionally, error handling for empty cgroup v1 values was removed, and the control flow in restrict-monit-api-access was updated to depend on the new helper function.

Suggested reviewers

• aramprice

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 50.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title 'fix cgroupsv1 support in warden' directly corresponds to the main change: reverting error-checking logic for cgroupsv1 support by implementing improved cgroup v2 detection and removing problematic error validation in the v1 branch.
Description check	✅ Passed	The pull request description clearly explains the motivation for reverting error-checking logic and references the specific GitHub issue being addressed.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch jammy-fix-cgroupsv1

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[rkoster]

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