refact ip stack (#11953)

roles/network_plugin/flannel/defaults/main.yml

@@ -2,7 +2,7 @@
 # Flannel public IP
 # The address that flannel should advertise as how to access the system
 # Disabled until https://github.com/coreos/flannel/issues/712 is fixed
-# flannel_public_ip: "{{ access_ip | default(ip | default(fallback_ip)) }}"
+# flannel_public_ip: "{{ main_access_ip }}"
 
 ## interface that should be used for flannel operations
 ## This is actually an inventory cluster-level item

roles/network_plugin/flannel/templates/cni-flannel.yml.j2

@@ -30,12 +30,14 @@ data:
     }
   net-conf.json: |
     {
+{% if ipv4_stack %}
       "Network": "{{ kube_pods_subnet }}",
       "EnableIPv4": true,
-{%   if enable_dual_stack_networks %}
+{% endif %}
+{% if ipv6_stack %}
       "EnableIPv6": true,
       "IPv6Network": "{{ kube_pods_subnet_ipv6 }}",
-{%   endif %}
+{% endif %}
       "Backend": {
         "Type": "{{ flannel_backend_type }}"{% if flannel_backend_type == "vxlan" %},
         "VNI": {{ flannel_vxlan_vni }},