Fix version check in rollback tests

[pchila]

What does this PR do?

Fix minimum version check to assert rollback reason when an elastic-agent upgrade is automatically rolled back.
PR #8407 didn't make it into 9.1 before the release branch was detached, so with the new version 9.1.0 being released, test TestStandaloneUpgradeRollback wrongly expected to find the rollback reason from a 9.1.0 elastic-agent status output.

Why is it important?

To have correct assertions for TestStandaloneUpgradeRollback integration tests.

Checklist

• I have read and understood the pull request guidelines of this project.
• 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/fragments using the changelog tool
• [ ] I have added an integration test or an E2E test

Disruptive User Impact

How to test this PR locally

Related issues

• Relates Preserve upgrade marker when rolling back and add rollback reason to upgrade details #8407

Questions to ask yourself

• How are we going to support this in production?
• How are we going to measure its adoption?
• How are we going to debug this?
• What are the metrics I should take care of?
• ...

[mergify]

This pull request does not have a backport label. Could you fix it @pchila? 🙏
To fixup this pull request, you need to add the backport labels for the needed
branches, such as:

• backport-./d./d is the label that automatically backports to the 8./d branch. /d is the digit
• backport-active-all is the label that automatically backports to all active branches.
• backport-active-8 is the label that automatically backports to all active minor branches for the 8 major.
• backport-active-9 is the label that automatically backports to all active minor branches for the 9 major.

[pchila]

CI run on top of the version bump PR #9172: https://buildkite.com/elastic/elastic-agent/builds/24573 (to verify that the issue is fixed).

Will rebase onto main and mark it ready for review.

[elastic-sonarqube]

Quality Gate passed

Issues
0 New issues
0 Fixed issues
0 Accepted issues

Measures
0 Security Hotspots
No data about Coverage
0.0% Duplication on New Code

See analysis details on SonarQube

[elasticmachine]

💚 Build Succeeded

• Buildkite Build
• Commit: ffdbefd

History

• 💛 Build #24573 was flaky 2d3de92

cc @pchila

[pkoutsovasilis]

LGTM, thanks for addressing that @pchila