Port to the tempest stable plugin interface (clients)

This is one of the last tempest plugins which was still not using
the proper interface to define its clients.
(Hopefully) no behavioral changes, just refactoring.

Change-Id: Ia57c771186cd1bf283f30b58007395d33aefa4a9
diff --git a/cinder_tempest_plugin/api/volume/base.py b/cinder_tempest_plugin/api/volume/base.py
index c0f53bd..1c64973 100644
--- a/cinder_tempest_plugin/api/volume/base.py
+++ b/cinder_tempest_plugin/api/volume/base.py
@@ -50,6 +50,9 @@
         cls.backups_client = cls.os_primary.backups_client_latest
         cls.volumes_client = cls.os_primary.volumes_client_latest
         cls.snapshots_client = cls.os_primary.snapshots_client_latest
+        cls.volume_revert_client = (
+            cls.os_primary.volume_revert_v3.VolumeRevertClient()
+        )
 
     @classmethod
     def setup_credentials(cls):
@@ -196,6 +199,9 @@
         cls.admin_volume_types_client = cls.os_admin.volume_types_client_latest
         cls.admin_backups_client = cls.os_admin.backups_client_latest
         cls.admin_volume_client = cls.os_admin.volumes_client_latest
+        cls.admin_consistencygroups_client = (
+            cls.os_admin.consistencygroups_v3.ConsistencyGroupsClient()
+        )
 
     @classmethod
     def create_volume_type(cls, name=None, **kwargs):