Trivial: Fix the pep8 warning

The yaml should start with "---"

Change-Id: I702cdf43afb6dffb8b7653e8c173f09dc8227bdc

examples/playbook.yml

@@ -1,3 +1,4 @@
+---
     - name: Installation and setup of Keystone
       hosts: keystone_all
       user: root

tasks/keystone_uwsgi.yml

@@ -1,3 +1,4 @@
+---
 # Copyright 2016, Rackspace US, Inc.
 #
 # Licensed under the Apache License, Version 2.0 (the "License");

tests/ansible-role-requirements.yml

@@ -1,3 +1,4 @@
+---
 - name: apt_package_pinning
   src: https://git.openstack.org/openstack/openstack-ansible-apt_package_pinning
   scm: git

zuul.d/project.yaml

@@ -1,3 +1,4 @@
+---
 # Copyright 2017, Rackspace US, Inc.
 #
 # Licensed under the Apache License, Version 2.0 (the "License");