Fix ntp time sync issue on Ubuntu 16.04

Note:
- ntpdate package needs to be installed explicity on Ubuntu. In CentOS,
this it is automatically pulled when ntp package is installed.
- stop ntp service after installation. In Ubuntu, ntp service is automatically
started after installation.

patch 2: combined ntpdate and ntp package installation code

Change-Id: Ieaccbb969cd2b8ad6e930a620947a192be5aa619
Closes-Bug: #1781092
(cherry picked from commit 98bf9c2)

playbooks/roles/configure_instances/tasks/ntp.yml

@@ -1,13 +1,19 @@
 ---
-- name: install ntpd
+- name: install ntp packages
   package:
-    name: ntp
+    name: "{{ item }}"
     state: latest
+  with_items:
+    - ntpdate
+    - ntp
 
 - name: set ntp service name
   set_fact:
     ntp_svc_name: "{{ 'ntp' if ansible_os_family == 'Debian' else 'ntpd' }}"
 
+- name: stop ntp service
+  service: name={{ ntp_svc_name }} state=stopped enabled=yes
+
 - name: set ntp server
   template:
     src: ntp.conf.j2