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/network_plugin/calico/templates/calico-crb.yml.j2

@@ -10,4 +10,4 @@ roleRef:
 subjects:
 - kind: ServiceAccount
   name: calico-node
-  namespace: {{ system_namespace }}
+  namespace: kube-system