Fix Ceph backed Nova snapshot

When both Glance and Nova are Ceph backed the instance snapshot
path can do a direct snapshot which leaves image bits in the Ceph
cluster.

At Newton and Ocata levels this requires show_multiple_locations=True
set in the glance API conf.  See [1].  Despite the Ceph doc stating
Mitaka also needs this, an OSA deployment of Mitaka has been found to
work without it.

Without this fix an OpenStack Ansible deployment wih Ceph
backed Nova and Glance will fail with symptoms as documented in [2].

A similar fix was put into DevStack under [3].

[1] http://docs.ceph.com/docs/master/rbd/rbd-openstack/#for-mitaka-only
[2] https://bugzilla.redhat.com/show_bug.cgi?id=1382737
[3] https://review.openstack.org/#/c/279630/

Change-Id: I52db9b5baf9209c72513da9c5f08e650ba6d43df

defaults/main.yml

@@ -60,6 +60,7 @@ glance_additional_stores:
   - cinder
 glance_flavor: "{% if glance_default_store == 'rbd' %}keystone{% else %}keystone+cachemanagement{% endif %}"
 glance_show_image_direct_url: "{{ glance_default_store == 'rbd' }}"
+glance_show_multiple_locations: "{{ glance_default_store == 'rbd' }}"
 
 
 ## API options

templates/glance-api.conf.j2

@@ -34,6 +34,7 @@ image_cache_dir = {{ glance_system_user_home }}/cache/
 
 # defaults to true if RBD is used as default store
 show_image_direct_url = {{ glance_show_image_direct_url }}
+show_multiple_locations = {{ glance_show_multiple_locations }}
 
 [task]
 task_executor = {{ glance_task_executor }}