Adding else in the inline if-expression (kubernetes-sigs#7292)

Fix "AnsibleUndefinedVariable: the inline if-expression on line xx evaluated to false and no else section was defined."

roles/kubernetes/control-plane/templates/kubeadm-config.v1beta2.yaml.j2

@@ -88,8 +88,8 @@ dns:
   imageTag: {{ coredns_image_tag }}
 networking:
   dnsDomain: {{ dns_domain }}
-  serviceSubnet: "{{ kube_service_addresses }}{{ ',' + kube_service_addresses_ipv6 if enable_dual_stack_networks }}"
-  podSubnet: "{{ kube_pods_subnet }}{{ ',' + kube_pods_subnet_ipv6 if enable_dual_stack_networks }}"
+  serviceSubnet: "{{ kube_service_addresses }}{{ ',' + kube_service_addresses_ipv6 if enable_dual_stack_networks else '' }}"
+  podSubnet: "{{ kube_pods_subnet }}{{ ',' + kube_pods_subnet_ipv6 if enable_dual_stack_networks else '' }}"
 {% if kube_feature_gates %}
 featureGates:
 {%   for feature in kube_feature_gates %}
@@ -133,7 +133,7 @@ apiServer:
     etcd-servers-overrides: "/events#{{ etcd_events_access_addresses_semicolon }}"
 {% endif %}
     service-node-port-range: {{ kube_apiserver_node_port_range }}
-    service-cluster-ip-range: "{{ kube_service_addresses }}{{ ',' + kube_service_addresses_ipv6 if enable_dual_stack_networks }}"
+    service-cluster-ip-range: "{{ kube_service_addresses }}{{ ',' + kube_service_addresses_ipv6 if enable_dual_stack_networks else '' }}"
     kubelet-preferred-address-types: "{{ kubelet_preferred_address_types }}"
     profiling: "{{ kube_profiling }}"
     request-timeout: "{{ kube_apiserver_request_timeout }}"
@@ -269,8 +269,8 @@ controllerManager:
   extraArgs:
     node-monitor-grace-period: {{ kube_controller_node_monitor_grace_period }}
     node-monitor-period: {{ kube_controller_node_monitor_period }}
-    cluster-cidr: "{{ kube_pods_subnet }}{{ ',' + kube_pods_subnet_ipv6 if enable_dual_stack_networks }}"
-    service-cluster-ip-range: "{{ kube_service_addresses }}{{ ',' + kube_service_addresses_ipv6 if enable_dual_stack_networks }}"
+    cluster-cidr: "{{ kube_pods_subnet }}{{ ',' + kube_pods_subnet_ipv6 if enable_dual_stack_networks else '' }}"
+    service-cluster-ip-range: "{{ kube_service_addresses }}{{ ',' + kube_service_addresses_ipv6 if enable_dual_stack_networks else '' }}"
 {% if enable_dual_stack_networks %}
     node-cidr-mask-size-ipv4: "{{ kube_network_node_prefix }}"
     node-cidr-mask-size-ipv6: "{{ kube_network_node_prefix_ipv6 }}"
@@ -363,7 +363,7 @@ clientConnection:
   contentType: {{ kube_proxy_client_content_type }}
   kubeconfig: {{ kube_proxy_client_kubeconfig }}
   qps: {{ kube_proxy_client_qps }}
-clusterCIDR: "{{ kube_pods_subnet }}{{ ',' + kube_pods_subnet_ipv6 if enable_dual_stack_networks }}"
+clusterCIDR: "{{ kube_pods_subnet }}{{ ',' + kube_pods_subnet_ipv6 if enable_dual_stack_networks else '' }}"
 configSyncPeriod: {{ kube_proxy_config_sync_period }}
 conntrack:
   maxPerCore: {{ kube_proxy_conntrack_max_per_core }}