PMM-12989 Reduce error logs from diagnostic data on arbiter nodes

[idoqo]

PMM-12989 (optional, if ticket reported)

• [ ] https://github.com/Percona-Lab/pmm-submodules/pull/3590

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Below we provide a basic checklist of things that would make it a good PR:

• Make sure to sign the CLA (Contributor License Agreement).
• Make sure all tests pass.
• Keep current with the target branch and fix conflicts if necessary.
• Update jira ticket description if necessary.
• Attach screenshots and/or console output to the jira ticket to confirm new behavior, if applicable.
• Leave notes to the reviewers if you need to focus their attention on something specific.

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