Fixes for CodeQL

[judysng]

Description of changes

CodeQL findings:

• In clusterstatusmgtd.py, adding a "return None" at the end to mitigate the implicit return. Case is not specified for what to return when the parameter "raise_on_error" is false when an error occurs, so returning an explicit None.
• Also fixed small typo in clusterstatusmgtd.py
• In cloudwatch_agent_config_util.py, added an explanatory comment for why there's a pass for a FileNotFoundError.

Going to Security > Code Scanning and typing "pr:2449" shows that the CodeQL alerts don't show up anymore!

References

• https://github.com/aws/aws-parallelcluster-cookbook/security/code-scanning/63
• https://github.com/aws/aws-parallelcluster-cookbook/security/code-scanning/62

Checklist

• Make sure you are pointing to the right branch.
• If you're creating a patch for a branch other than develop add the branch name as prefix in the PR title (e.g. [release-3.6]).
• Check all commits' messages are clear, describing what and why vs how.
• Make sure to have added unit tests or integration tests to cover the new/modified code.
• Check if documentation is impacted by this change.

Please review the guidelines for contributing and Pull Request Instructions.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[codecov]

Codecov Report

Patch coverage: 66.66% and project coverage change: -0.04% ⚠️

Comparison is base (3570025) 70.53% compared to head (3f789db) 70.49%.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #2449      +/-   ##
===========================================
- Coverage    70.53%   70.49%   -0.04%     
===========================================
  Files           13       13              
  Lines         1863     1864       +1     
===========================================
  Hits          1314     1314              
- Misses         549      550       +1     

Flag	Coverage Δ
unittests	70.49% <66.66%> (-0.04%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files Changed	Coverage Δ
...fleet/files/clusterstatusmgtd/clusterstatusmgtd.py	74.70% <66.66%> (-0.30%)	⬇️

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[himani2411]

Could you add more descriptive commit messages.

[himani2411]

Also, Can you have a look at which unit tests might be covering the tests as there are codecov checks which mention that the coverage is reduced.