Do not try to run etcd in serial mode

Etcd static discovery, even in bootstrap mode, tries to wait for all
members to join. Until that systemd unit is in `activating` state which
means that task just timeouts waiting for activation. So etcd can not be
run in serial.

With that we also move etcd installation from zun role to the playbook.
As we still want to run playbook for zun installation/configuration in
serial mode, having etcd in independent play allows us to
do that.

This partially reverts commit Ie996262043edb8fb9c7221a5cd98e98a0111ac28

Change-Id: Ic621a7618b99abb56d24e4dcbb52b495c1b39d57

playbooks/etcd-install.yml

@@ -22,7 +22,7 @@
 - name: Install etcd server cluster
   hosts: etcd
   gather_facts: false
-  serial: "{{ etcd_serial | default(1) }}"
+  serial: "{{ etcd_serial | default('100%') }}"
   user: root
   pre_tasks:
     - include_tasks: "common-tasks/os-{{ container_tech | default('lxc') }}-container-setup.yml"

playbooks/os-zun-install.yml

@@ -23,6 +23,19 @@
   tags:
     - always
 
+- name: Install etcd cluster
+  hosts: zun_api
+  gather_facts: false
+  serial: "{{ etcd_serial | default('100%') }}"
+  roles:
+    - role: "etcd"
+      vars:
+        etcd_cluster_group: "zun_api"
+        etcd_install_type: server
+  tags:
+    - zun-install
+    - etcd-server
+
 - name: Install the zun components
   hosts: zun_all
   gather_facts: false