kinder: update super-admin workflow for 1.30

[neolit123]

xref #2414 (comment)

kubeadm 1.29 had code that creates the super-admin.conf file on upgrade. the same code is removed in kubeadm 1.30. Update the super-admin kinder workflow to reflect this change.

[neolit123]

self lgtm to try to fix CI

[pacoxu]

/lgtm
miss this

[k8s-ci-robot]

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[pacoxu]

https://storage.googleapis.com/kubernetes-jenkins/logs/ci-kubernetes-e2e-kubeadm-kinder-super-admin-latest/1755150059663527936/artifacts/task-09-post-upgrade-primary-cp-log.txt
last run still failed with this PR.

# admin.conf must exist, super-admin.conf must not exist as we deleted it after init
${CMD} test -f /etc/kubernetes/admin.conf || exit 1
${CMD} test -f /etc/kubernetes/super-admin.conf && exit 1

https://prow.k8s.io/view/gs/kubernetes-jenkins/logs/ci-kubernetes-e2e-kubeadm-kinder-super-admin-latest/1755150059663527936

[pacoxu]

Last error was addressed, and this is a new one just after it.

grep: /etc/kubernetes/super-admin.conf: No such file or directory
Could not read certificate from <stdin>
Unable to load certificate
+ exit 1

The next line needs an update as well.

${CMD} grep 'client-certificate-data' /etc/kubernetes/super-admin.conf | awk '{print $2}' | base64 -d | openssl x509 -subject -noout | grep "subject=O = system:masters, CN = kubernetes-super-admin" || exit 1

[neolit123]

right, i missed that one.
will send new PR a bit later.

[neolit123]

Last error was addressed, and this is a new one just after it.

grep: /etc/kubernetes/super-admin.conf: No such file or directory
Could not read certificate from <stdin>
Unable to load certificate
+ exit 1

The next line needs an update as well.

${CMD} grep 'client-certificate-data' /etc/kubernetes/super-admin.conf | awk '{print $2}' | base64 -d | openssl x509 -subject -noout | grep "subject=O = system:masters, CN = kubernetes-super-admin" || exit 1

here is the PR
https://github.com/kubernetes/kubeadm/pull/3015/files