PMM-12350 Reduce error logs from diagnostic data on arbiter nodes

PMM-12350 (optional, if ticket reported)

[ ] Links to related pull requests (optional).

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.
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percona / mongodb_exporter

PMM-12350 Reduce error logs from diagnostic data on arbiter nodes #819