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/network_plugin/cilium/tasks/apply.yml

@@ -11,7 +11,7 @@
   when: inventory_hostname == groups['kube_control_plane'][0] and not item is skipped
 
 - name: Cilium | Wait for pods to run
-  command: "{{ bin_dir }}/kubectl -n kube-system get pods -l k8s-app=cilium -o jsonpath='{.items[?(@.status.containerStatuses[0].ready==false)].metadata.name}'"  # noqa 601
+  command: "{{ kubectl }} -n kube-system get pods -l k8s-app=cilium -o jsonpath='{.items[?(@.status.containerStatuses[0].ready==false)].metadata.name}'"  # noqa 601
   register: pods_not_ready
   until: pods_not_ready.stdout.find("cilium")==-1
   retries: 30