[ntp] Add role documentation in sphinx

This patch adds the documentation directly in the sphinx role
documentation index. All variables have been commented with a proper
description to be included automatically in the sphinx build.

This patch also disable the facts gathering because this validation
doesn't need them and only uses service_facts in the ntp role.

Change-Id: I3a19eb0a93f6dfaaf7a4361b46b2dc904aeb7ae6
Signed-off-by: Gael Chamoulaud (Strider) <gchamoul@redhat.com>

doc/source/roles/role-ntp.rst

@@ -2,5 +2,45 @@
 ntp
 ===
 
+--------------
+About The Role
+--------------
+
+An Ansible role to check if the host(s) have their clock synchronized.
+
+Requirements
+============
+
+No requirements.
+
+Dependencies
+============
+
+No dependencies.
+
+Example Playbook
+================
+
+.. code-block:: yaml
+
+   - hosts: localhost
+     gather_facts: false
+     roles:
+       - ntp
+
+License
+=======
+
+Apache
+
+Author Information
+==================
+
+**Red Hat TripleO DFG:DF Squad:VF**
+
+----------------
+Full Description
+----------------
+
 .. ansibleautoplugin::
    :role: validations_common/roles/ntp

validations_common/playbooks/ntp.yaml

@@ -1,5 +1,6 @@
 ---
 - hosts: localhost
+  gather_facts: false
   vars:
     metadata:
       name: Verify all deployed servers have their clock synchronised