kubeadm config validate flag for debugging and development (#12001)

This adds a new flag with default `kubeadm_config_validate_enabled: true` to use when debugging features and enhancements affected by the `kubeadm config validate command`.

This new flag should be set to `false` only for development and testing scenarios where validation is expected to fail (pre-release Kubernetes versions, etc).

While working with development and test versions of Kubernetes and Kubespray, I found this option very useful.

roles/kubernetes/kubeadm/tasks/kubeadm_etcd_node.yml

@@ -9,7 +9,7 @@
     src: "kubeadm-client.conf.j2"
     dest: "{{ kube_config_dir }}/kubeadm-cert-controlplane.conf"
     mode: "0640"
-    validate: "{{ bin_dir }}/kubeadm config validate --config %s"
+    validate: "{{ kubeadm_config_validate_enabled | ternary(bin_dir + '/kubeadm config validate --config %s', omit) }}"
   vars:
     kubeadm_cert_controlplane: true
 

roles/kubernetes/kubeadm/tasks/main.yml

@@ -75,7 +75,7 @@
     dest: "{{ kube_config_dir }}/kubeadm-client.conf"
     backup: true
     mode: "0640"
-    validate: "{{ bin_dir }}/kubeadm config validate --config %s"
+    validate: "{{ kubeadm_config_validate_enabled | ternary(bin_dir + '/kubeadm config validate --config %s', omit) }}"
   when: ('kube_control_plane' not in group_names)
 
 - name: Join to cluster if needed