fix: cloud-init clean --logs should not remove non-files

[blackboxsw]

Proposed Commit Message

Add test coverage for the fix that prevents cloud-init clean --logs
from attempting to remove non-file paths (e.g., character devices,
directories) that may appear in the log file configuration.

The test verifies that when /dev/null is configured as a log path,
it is safely skipped while actual log files are still removed.

Additional Context

Test Steps

 tox -e py3 -- tests/unittests/cmd/test_clean.py::TestClean::test_remove_artifacts_skips_non_file_logs

Merge type

• [x] Squash merge using "Proposed Commit Message"
• [ ] Rebase and merge unique commits. Requires commit messages per-commit each referencing the pull request number (#<PR_NUM>)

[blackboxsw]

Thanks for this @blackboxsw. I left a couple of comments. Also, can you share the error you saw?

@holmanb here is the error which could be caused be custom /etc/cloud/cloud.cfg.d/05_logging.cfg changing log files to character devices or symlinks.

root@dd:~# cloud-init clean --logs
Traceback (most recent call last):
  File "/usr/bin/cloud-init", line 9, in <module>
    sys.exit(main.main())
             ~~~~~~~~~^^
  File "/usr/lib/python3/dist-packages/cloudinit/cmd/main.py", line 1308, in main
    return sub_main(args, parser)
  File "/usr/lib/python3/dist-packages/cloudinit/cmd/main.py", line 1438, in sub_main
    retval = functor(name, args)
  File "/usr/lib/python3/dist-packages/cloudinit/cmd/clean.py", line 189, in handle_clean_args
    exit_code = remove_artifacts(
        init, args.remove_logs, args.remove_seed, args.remove_config
    )
  File "/usr/lib/python3/dist-packages/cloudinit/cmd/clean.py", line 129, in remove_artifacts
    del_file(log_file)
    ~~~~~~~~^^^^^^^^^^
  File "/usr/lib/python3/dist-packages/cloudinit/util.py", line 2072, in del_file
    os.unlink(path)
    ~~~~~~~~~^^^^^^
OSError: [Errno 16] Device or resource busy: '/dev/console'