This patch replaces bash-specific [[ ... ]] expressions in the
run_kubernetes_test function with POSIX-compliant case and test
constructs. It ensures that the Kubernetes version on each worker node
is verified correctly and that required components (CoreDNS, Cilium,
ingress-nginx, vsnap-crd) are ready before proceeding. Now the tests
work reliably even when executed with /bin/sh, such as in Bats.
```release-note
[tests] Make Kubernetes tests POSIX-compliant and more reliable:
verify worker node versions and ensure required releases (CoreDNS,
Cilium, ingress-nginx, vsnap-crd) are installed and ready.
```
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## What this PR does
### Release note
<!-- Write a release note:
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```release-note
[]
```
<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit
* **Bug Fixes**
* Improved Kubernetes version detection to correctly handle 1.32
variants.
* Made node readiness checks more reliable to reduce false failures
during runs.
* **Refactor**
* Streamlined version matching logic for clearer, more predictable
behavior across releases.
* **Style**
* Minor formatting cleanups with no functional impact.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->