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/remove-node/remove-etcd-node/tasks/main.yml

@@ -1,8 +1,8 @@
 ---
 - name: Lookup node IP in kubernetes
-  shell: >-
-    {{ bin_dir }}/kubectl get nodes {{ node }}
-    -o jsonpath='{range.status.addresses[?(@.type=="InternalIP")]}{.address}{"\n"}{end}'
+  command: >
+    {{ kubectl }} get nodes {{ node }}
+    -o jsonpath={range.status.addresses[?(@.type=="InternalIP")]}{.address}{"\n"}{end}
   register: remove_node_ip
   when:
     - inventory_hostname in groups['etcd']