Revert "etcd: enable v2 api only if needed (#8001)" (#8008)

This reverts commit c0e1211a.

roles/etcd/templates/etcd.env.j2

@@ -32,9 +32,8 @@ ETCD_MAX_SNAPSHOTS={{ etcd_max_snapshots }}
 {% if etcd_max_wals is defined %}
 ETCD_MAX_WALS={{ etcd_max_wals }}
 {% endif %}
-{% if hostvars[groups['k8s_cluster'][0]]['kube_network_plugin'] == 'flannel' %}
+# Flannel need etcd v2 API
 ETCD_ENABLE_V2=true
-{% endif %}
 
 # TLS settings
 ETCD_TRUSTED_CA_FILE={{ etcd_cert_dir }}/ca.pem