Metricbeat, fix metricsets log level behavior

[philippkahr]

What does this PR do?

Until now errors in the metric sets were only reported as INFO. If someone configures metricbeat to only write a log file on error, issues like cannot connect to Elasticsearch 404, 400 Bad request could be missed.

Why is it important?

• Easier debugging
• If metricbeat cannot connect it is an error and should be classified as such a thing.

Checklist

• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have made corresponding change to the default configuration files
• I have added tests that prove my fix is effective or that my feature works
• I have added an entry in CHANGELOG.next.asciidoc or CHANGELOG-developer.next.asciidoc.

Related issues

• Closes Metricbeat metric sets modules uses wrong log level #27799
• Had some issues with Git in this one Metricbeat, fix metricsets log level behavior #27803

[botelastic]

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[elasticmachine]

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• Start Time: 2021-09-08T09:29:31.836+0000

• Duration: 124 min 59 sec

• Commit: 553e2c3

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Failed	0
Passed	17639
Skipped	2768
Total	20407

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Test stats 🧪

Test	Results
Failed	0
Passed	17639
Skipped	2768
Total	20407

[jsoriano]

Thanks! 👍