Add the "---" into ansible yaml file

Change-Id: If4e684da58bffbe25d5bbed4dd4c56d0b5345114
Story: #2003783
Task: #26488

playbooks/integration/centos-image.yaml

@@ -1,3 +1,4 @@
+---
 - hosts: all
   environment:
     OS_CLOUD: devstack-admin

playbooks/integration/cirros-image.yaml

@@ -1,3 +1,4 @@
+---
 - name: Find Cirros UEC image
   shell: openstack image list -f value -c Name | grep 'cirros-.*-uec$'
   register: cirros_uec_image_result

playbooks/integration/exercise.yaml

@@ -1,3 +1,4 @@
+---
 - name: Create a port
   command: openstack port create --network private test-port
   when: metalsmith_precreate_port

playbooks/integration/post.yaml

@@ -1,3 +1,4 @@
+---
 - hosts: all
   tasks:
     - name: Check that VM logs exist

playbooks/integration/pre.yaml

@@ -1,3 +1,4 @@
+---
 - hosts: all
   roles:
     - run-devstack

playbooks/integration/run.yaml

@@ -1,3 +1,4 @@
+---
 - hosts: all
   environment:
     OS_CLOUD: devstack-admin

playbooks/integration/ssh-key.yaml

@@ -1,3 +1,4 @@
+---
 - name: Find a public SSH key file
   find:
     path: ~/.ssh/