Add example playbbok

Add playbook as an example, since it was included in docs,
but was empty.

Change-Id: I342dd945b823b2b8134d759df2e2e2dd06a74ad4

examples/playbook.yml

@@ -0,0 +1,12 @@
+- name: Install placement components
+  hosts: placement_all
+  gather_facts: "{{ osa_gather_facts | default(True) }}"
+  environment: "{{ deployment_environment_variables | default({}) }}"
+  user: root
+  tags:
+    - placement
+  roles:
+    - role: "os_placement"
+    - role: "system_crontab_coordination"
+      tags:
+        - crontab