kubeadm: remove 'system:masters' organization from apiserver-etcd-client certificate

[SataQiu]

What type of PR is this?

/kind cleanup

What this PR does / why we need it:

kubeadm: remove 'system:masters' organization from apiserver-etcd-client certificate.
system:masters organization does not make sense for kube-apiserver to connect to etcd.

Which issue(s) this PR fixes:

Fixes kubernetes/kubeadm#2926

Special notes for your reviewer:

• We also need to update the documentation https://kubernetes.io/docs/setup/best-practices/certificates/#all-certificates remove "O=system:masters" from "kube-apiserver-etcd-client".md website#42942

Does this PR introduce a user-facing change?

kubeadm: remove 'system:masters' organization from apiserver-etcd-client certificate

Additional documentation e.g., KEPs (Kubernetes Enhancement Proposals), usage docs, etc.:

[k8s-ci-robot]

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[neolit123]

thanks, odd if we don't have tests for these.

/lgtm

[k8s-ci-robot]

LGTM label has been added.

Git tree hash: 18462ffcd13feb4ed977f0924501ba8dc24a3155

[pacoxu]

/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: pacoxu, SataQiu

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• cmd/kubeadm/OWNERS [SataQiu,pacoxu]

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