Check node_ip is defined when removing etcd node (#6603)

roles/remove-node/remove-etcd-node/tasks/main.yml

@@ -17,6 +17,11 @@
   when:
     - inventory_hostname in groups['etcd']
 
+- name: Make sure node_ip is set
+  assert:
+    that: node_ip is defined and node_ip | length > 0
+    msg: "Etcd node ip is not set !"
+
 - name: Lookup etcd member id
   shell: "{{ bin_dir }}/etcdctl member list | grep {{ node_ip }} | cut -d, -f1"
   register: etcd_member_id