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/kubespray-defaults/defaults/main.yaml

@@ -61,7 +61,6 @@ dns_domain: "{{ cluster_name }}"
 kube_config_dir: /etc/kubernetes
 kube_script_dir: "{{ bin_dir }}/kubernetes-scripts"
 kube_manifest_dir: "{{ kube_config_dir }}/manifests"
-system_namespace: kube-system
 
 # This is where all the cert scripts and certs will be located
 kube_cert_dir: "{{ kube_config_dir }}/ssl"