Allow more configuration of Cinder Ceph backends

Allow the pool and user of each Ceph backend in Cinder to be customised.
Defaults are provided to keep existing behaviour when these are not
defined.

Author: MoteHue

ansible/roles/cinder/templates/cinder.conf.j2

@@ -163,12 +163,12 @@ target_protocol = iscsi
 [{{ backend.name }}]
 volume_driver = cinder.volume.drivers.rbd.RBDDriver
 volume_backend_name = {{ backend.name }}
-rbd_pool = {{ ceph_cinder_pool_name }}
+rbd_pool = {{ backend.pool | default(ceph_cinder_pool_name) }}
 rbd_ceph_conf = /etc/ceph/{{ backend.cluster }}.conf
 rados_connect_timeout = 5
-rbd_user = {{ ceph_cinder_user }}
+rbd_user = {{ backend.user | default(ceph_cinder_user) }}
 rbd_cluster_name = {{ backend.cluster }}
-rbd_keyring_conf = /etc/ceph/{{ backend.cluster }}.{{ ceph_cinder_keyring }}
+rbd_keyring_conf = /etc/ceph/{{ backend.cluster }}.{{ ('client.' + backend.user + '.keyring') if backend.user is defined else ceph_cinder_keyring }}
 rbd_secret_uuid = {{ cinder_rbd_secret_uuid }}
 report_discard_supported = True
 {% if backend.availability_zone is defined %}