[DFSM] Support live updates on compute nodes.

[gmarciani]

Description of changes

Add support for live updates on compute nodes, using cfn-hup. In particular:

• added cfn-hup to supervisord programs in compute fleet.
• emit dummy log line to prove that update is triggered in compute nodes.

This PR is related to aws/aws-parallelcluster#6003, where the cfn-hup config file is created.

Tests

• Adapted rspec tests to cover the changes.
• Manual testing: cluster creation + forced update verifying that the update succeeds and the log line is emitted.

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

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (ef5d05f) 75.56% compared to head (fbd2e29) 75.56%.

❗ Current head fbd2e29 differs from pull request most recent head ffd9c73. Consider uploading reports for the commit ffd9c73 to get more accurate results

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #2614   +/-   ##
========================================
  Coverage    75.56%   75.56%           
========================================
  Files           16       16           
  Lines         2132     2132           
========================================
  Hits          1611     1611           
  Misses         521      521           

Flag	Coverage Δ
unittests	75.56% <ø> (ø)

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

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.