Use CNI to assign kube_pods_subnet for calico

Now calico can be deployed if there are other existing pools
and not confuse IPAM and end up with pods in the wrong pools.

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

@@ -15,16 +15,18 @@
       "etcd_ca_cert_file": "{{ etcd_cert_dir }}/ca.pem",
       "log_level": "info",
       "ipam": {
-        "type": "calico-ipam"
+        "type": "calico-ipam",
+        "assign_ipv4": "true",
+        "ipv4_pools": ["{{ kube_pods_subnet }}"]
       },
     {% if enable_network_policy %}
       "policy": {
         "type": "k8s"
       },
-    {% endif %}
+    {%- endif %}
     {% if calico_mtu is defined and calico_mtu is number %}
       "mtu": {{ calico_mtu }},
-    {% endif %}
+    {%- endif %}
       "kubernetes": {
         "kubeconfig": "{{ kube_config_dir }}/node-kubeconfig.yaml"
       }