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-sa.yml.j2

@@ -3,4 +3,4 @@ apiVersion: v1
 kind: ServiceAccount
 metadata:
   name: cilium
-  namespace: {{ system_namespace }}
+  namespace: kube-system