Stop templating kube-system namespace and creating it (#2545)

Kubernetes makes this namespace automatically, so there is
no need for kubespray to manage it.

roles/kubernetes-apps/cluster_roles/templates/namespace.j2

@@ -1,4 +1,4 @@
 apiVersion: v1
 kind: Namespace
 metadata:
-  name: "{{system_namespace}}"
+  name: "kube-system"