cks: use kubeadm v1beta4 configuration API for external etcd clusters

The control node's /etc/kubernetes/kubeadm-config.yaml was written with the
kubeadm.k8s.io/v1beta3 configuration API. kubeadm removed v1beta3 in Kubernetes
1.37, so "kubeadm init --config" now rejects the file outright:

  error: your configuration file uses an old API spec: "kubeadm.k8s.io/v1beta3"
  (kind: "ClusterConfiguration"). Please use kubeadm v1.36 instead and run
  'kubeadm config migrate --old-config old-config-file --new-config new-config-file',
  which will write the new, similar spec using a newer API version.
  Error: kubeadm init failed!

This only affects clusters created with external etcd nodes, as that is the only
path which passes the configuration file to kubeadm; the stacked etcd path and
both join paths use command line flags and are unaffected.

The failure is also hard to spot: kubeadm init runs from the deploy-kube-system
systemd unit, runcmd only does "systemctl start" on a Type=simple unit so
cloud-init reports success, and Restart=on-failure with StartLimitInterval=0
retries the whole cycle indefinitely.

Switch both documents to v1beta4. Only the apiVersion changes - neither document
sets the extraArgs fields whose shape changed between the two versions.

Tested on Kubernetes v1.37.0 (KVM): an external etcd cluster which previously
failed at kubeadm init now completes and the control plane comes up.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

Author: kiranchavala

plugins/integrations/kubernetes-service/src/main/resources/conf/k8s-control-node.yml

@@ -246,7 +246,7 @@ write_files:
     permissions: '0644'
     owner: root:root
     content: |
-      apiVersion: kubeadm.k8s.io/v1beta3
+      apiVersion: kubeadm.k8s.io/v1beta4
       kind: ClusterConfiguration
       apiServer:
         certSANs:
@@ -257,7 +257,7 @@ write_files:
           endpoints:
           {{ etcd.etcd_endpoint_list }}
       ---
-      apiVersion: kubeadm.k8s.io/v1beta3
+      apiVersion: kubeadm.k8s.io/v1beta4
       kind: InitConfiguration
       bootstrapTokens:
         - token: "{{ k8s_control_node.cluster.token }}"