Improve etcd scale up (#1846)

Now adding unjoined members to existing etcd cluster
occurs one at a time so that the cluster does not
lose quorum.

roles/etcd/tasks/configure.yml

@@ -9,10 +9,6 @@
   tags:
     - facts
 
-- name: Configure | Add member to the cluster if it is not there
-  when: is_etcd_master and etcd_member_in_cluster.rc != 0 and etcd_cluster_is_healthy.rc == 0
-  shell: "{{ bin_dir }}/etcdctl --peers={{ etcd_access_addresses }} member add {{ etcd_member_name }} {{ etcd_peer_url }}"
-
 - name: Install etcd launch script
   template:
     src: etcd.j2
@@ -29,3 +25,12 @@
     backup: yes
   when: is_etcd_master
   notify: restart etcd
+
+- name: Configure | Join member(s) to cluster one at a time
+  include: join_member.yml
+  vars:
+    target_node: "{{ item }}"
+  loop_control:
+    pause: 10
+  with_items: "{{ groups['etcd'] }}"
+  when: inventory_hostname == item and etcd_member_in_cluster.rc != 0 and etcd_cluster_is_healthy.rc == 0