Group cinder-volume services using cluster config

Usage of "host" config for grouping cinder-volume
services for the purpose of stateless config and/or
active-active HA is not recommended.

The usage of "cluster" config is recommended for
achieving that behavior. This change replaces the
usage of "host" with "cluster".

Change-Id: I249ce179cfdaf2394ee4e8481a8c9644d667ea99
Closes-bug: #1945239

hooks/cinder_contexts.py

@@ -194,10 +194,18 @@ class CinderSubordinateConfigContext(SubordinateConfigContext):
                 any_stateless = any_stateless or stateless
 
         if stateless:
+
+            cmp_os_release = CompareOpenStackReleases(
+                os_release('cinder-common'))
+            clustering_config = ('cluster' if cmp_os_release >= "ocata"
+                                 else 'host')
+
             if 'DEFAULT' in ctxt['sections']:
-                ctxt['sections']['DEFAULT'].append(('host', service_name()))
+                ctxt['sections']['DEFAULT'].append(
+                    (clustering_config, service_name()))
             else:
-                ctxt['sections']['DEFAULT'] = [('host', service_name())]
+                ctxt['sections']['DEFAULT'] = [
+                    (clustering_config, service_name())]
 
         elif any_stateless:
             log("One or more stateless backends configured but unable to "

unit_tests/test_cinder_contexts.py

@@ -312,6 +312,23 @@ class TestCinderContext(CharmTestCase):
 
         mock_rel_get.side_effect = fake_rel_get
         self.relation_get.side_effect = fake_rel_get
+        self.os_release.return_value = 'ocata'
+
+        ctxt = contexts.CinderSubordinateConfigContext(
+            interface='storage-backend',
+            service='cinder',
+            config_file='/etc/cinder/cinder.conf')()
+
+        exp = {'sections': {'DEFAULT': [('cluster', 'cinder')],
+               u'cinder-ceph': [[u'volume_backend_name', u'cinder-ceph'],
+                                [u'volume_driver',
+                                 u'cinder.volume.drivers.rbd.RBDDriver'],
+                                [u'rbd_pool', u'cinder-ceph'],
+                                [u'rbd_user', u'cinder-ceph']]}}
+
+        self.assertEqual(ctxt, exp)
+
+        self.os_release.return_value = 'newton'
 
         ctxt = contexts.CinderSubordinateConfigContext(
             interface='storage-backend',