Add documentation about having HA for etcd

roles/etcd/tasks/gen_certs_vault.yml

@@ -26,6 +26,9 @@
         "{{ hostvars[host]['ip'] }}",
         {%- endif -%}
         {%- endfor -%}
+        {%- for cert_alt_ip in etcd_cert_alt_ips -%}
+        "{{ cert_alt_ip }}",
+        {%- endfor -%}
         "127.0.0.1","::1"
         ]
     issue_cert_path: "{{ item }}"