ci: Use prev k8s version for upgrade e2e test

[gracedo]

What problem does this PR solve?:
Made the change to use the same k8s version for upgrade tests since the previous version is compatible on 1.26

Held off on updating to 1.27 because it looks like there were issues with getting that build working in CI

depends on #1455

Which issue(s) does this PR fix?:

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

Checklist

• If the PR adds a version bump, ensure there is no breaking change in Licensing model (or NA).
• If a chart is changed or app configuration is significantly changed, the chart version is correctly incremented (so that apps are not automatically upgraded from a previous version of DKP).

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[coveralls]

Pull Request Test Coverage Report for Build 5741220016

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 79.532%

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Totals
Change from base Build 5740918391:	0.0%
Covered Lines:	136
Relevant Lines:	171

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💛 - Coveralls

[jimmidyson]

This is a tricky one because we do actually still install kommander on previous kubernetes version before kube version upgrade. That is the supported upgrade process afaik. We should probably test upgrading from both previous k8s version, and current version. Wdyt @gracedo?

[gracedo]

This is a tricky one because we do actually still install kommander on previous kubernetes version before kube version upgrade. That is the supported upgrade process afaik. We should probably test upgrading from both previous k8s version, and current version. Wdyt @gracedo?

Hmm, you're right that it would be more accurate to use the previous k8s version for the upgrade test, because k-apps are upgraded first before upgrading k8s (at least for now). Although the main focus of the test here is to test the application upgrades (not too much focus on k8s version) we might as well mimic the actual upgrade scenario since it is easy to here. Install tests will still happen on current k8s version, upgrade tests will happen on previous k8s version.

[gracedo]

I believe it's already been seen that current version gatekeeper is not compatible with 1.27 so the tests may fail -- will revert the last commit (trying out 1.27) if I see the same. Will let https://d2iq.atlassian.net/browse/D2IQ-98552 take care of the bump