Add volume backup description parameter

Update "test_volume_backup_create_get_detailed_list_restore_delete"
testcase to verifiy volume backup description parameter.

Change-Id: Ib8de9029d61cbce8519eafa38d98428fa7155ea6
diff --git a/tempest/api/volume/test_volumes_backup.py b/tempest/api/volume/test_volumes_backup.py
index 972dd58..0091027 100644
--- a/tempest/api/volume/test_volumes_backup.py
+++ b/tempest/api/volume/test_volumes_backup.py
@@ -38,8 +38,10 @@
                         volume['id'])
         backup_name = data_utils.rand_name(
             self.__class__.__name__ + '-Backup')
+        description = data_utils.rand_name("volume-backup-description")
         backup = self.create_backup(volume_id=volume['id'],
-                                    name=backup_name)
+                                    name=backup_name,
+                                    description=description)
         self.assertEqual(backup_name, backup['name'])
         waiters.wait_for_volume_status(self.volumes_client,
                                        volume['id'], 'available')
@@ -47,6 +49,7 @@
         # Get a given backup
         backup = self.backups_client.show_backup(backup['id'])['backup']
         self.assertEqual(backup_name, backup['name'])
+        self.assertEqual(description, backup['description'])
 
         # Get all backups with detail
         backups = self.backups_client.list_backups(