Fix possible problems with legacy calicoctl

When running legacy calicoctl we do not specify calico hostname in
calico-node container thus we should not specify it in CNI config.

Also move 'legacy_calicoctl' set_fact task to the top.

roles/network_plugin/calico/templates/cni-calico.conf.j2

@@ -1,6 +1,8 @@
 {
   "name": "calico-k8s-network",
+{% if not legacy_calicoctl %}
   "hostname": "{{ inventory_hostname }}",
+{% endif %}
   "type": "calico",
   "etcd_endpoints": "{{ etcd_access_endpoint }}",
   "etcd_cert_file": "{{ etcd_cert_dir }}/node.pem",