Makefile: Update Cockpit lib to 3cd180202d09c34b1

[github-actions[bot]]

Adjust to the select_PF() testlib API change.

• [x] https://github.com/cockpit-project/cockpit/pull/20790

[martinpitt]

This will fail, I have a local fix.

[martinpitt]

Ach, dang -- that feels like "old cockpit shell", I may have dropped that fallback too early. → Monday