Use a variable for standardizing kubectl invocation (#8329)

* Add kubectl variable

* Replace kubectl usage by kubectl variable in roles

* Remove redundant --kubeconfig on kubectl usage

* Replace unecessary shell usage with command

roles/kubernetes/node-label/tasks/main.yml

@@ -42,7 +42,7 @@
 
 - name: Set label to node
   command: >-
-      {{ bin_dir }}/kubectl label node {{ kube_override_hostname | default(inventory_hostname) }} {{ item }} --overwrite=true
+      {{ kubectl }} label node {{ kube_override_hostname | default(inventory_hostname) }} {{ item }} --overwrite=true
   loop: "{{ role_node_labels + inventory_node_labels }}"
   delegate_to: "{{ groups['kube_control_plane'][0] }}"
   changed_when: false