CRAYSAT-1895: add empty string handling for rootfs_provider key of boot_set

[ethanholen-hpe]

Summary and Scope

This PR adds validation to check that rootfs_provider and rootfs_provider_passthrough are not empty strings

Issues and Related PRs

• Resolves CRAYSAT-1895

Testing

Tested on:

• drax

Test description:

Changes were successful, output of testing on drax: https://gist.github.com/ethanholen-hpe/7069d94e25dc06c59ba84c05c04cfb07#file-gistfile1-txt

Pull Request Checklist

• Version number(s) incremented, if applicable
• Copyrights updated
• License file intact
• Target branch correct
• CHANGELOG.md updated
• Testing is appropriate and complete, if applicable
• HPC Product Announcement prepared, if applicable

[ethanholen-hpe]

Testing output on Drax: https://gist.github.com/ethanholen-hpe/7069d94e25dc06c59ba84c05c04cfb07#file-gistfile1-txt

[ethanholen-hpe]

Testing output without change on drax: https://gist.github.com/ethanholen-hpe/16af8f07515668d0ea78ec3ae17d0206
Output with change on drax: https://gist.github.com/ethanholen-hpe/339f4a2aeee9707db6c024ba27a0b49f

[haasken-hpe]

When you squash your commits prior to merging, please use a format like the following for your commit message:

<JIRA_ISSUE_ID>: Short description of change

Longer description of change.

See other commits in this repo for an example. I also have a local Git prepare-commit-msg hook that automatically populates the commit message with the Jira ID from the branch. I can share that with you if you're interested.

As far as what makes a good commit message, I like to refer people to these guidelines. I don't care too much about the strict line length limits, especially for the subject line, but I agree with the other points.

[annapoorna-s-alt]

This looks good to me. Can we update the unit tests as well?

[ethanholen-hpe]

/backport release/3.32

[github-actions]

Backporting into branch release/3.32 was successful. New PR: #289