Change log level to warning instead of error when cgroups file read f…

[nekop]

…ailed.

Because cgroups file may not exist at the timing of the read, it's better not to use error level.

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[k8s-ci-robot]

Hi @nekop. Thanks for your PR.

I'm waiting for a google or kubernetes member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

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Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[nekop]

I signed it!

[googlebot]

CLAs look good, thanks!

[dashpole]

/ok-to-test

[dashpole]

Because cgroups file may not exist at the timing of the read

Can you describe such a case?

[nekop]

Can you describe such a case?

When a container and the cgroups removed before read the file. This error log appears multiple times every day in healthy k8s clusters.

[dashpole]

lgtm