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/ansible/templates/kubedns-autoscaler-sa.yml.j2

@@ -17,4 +17,4 @@ kind: ServiceAccount
 apiVersion: v1
 metadata:
   name: cluster-proportional-autoscaler
-  namespace: {{ system_namespace }}
+  namespace: kube-system