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/cilium/templates/cilium-crb.yml.j2

@@ -10,6 +10,6 @@ roleRef:
 subjects:
 - kind: ServiceAccount
   name: cilium
-  namespace: {{ system_namespace }}
+  namespace: kube-system
 - kind: Group
   name: system:nodes