'Make a Volume representation compatible with a target version.'

def obj_make_compatible(self, primitive, target_version):

    added_fields = (((1, 4), ('cluster', 'cluster_name')), ((1, 5), ('group', 'group_id')))
    super(Volume, self).obj_make_compatible(primitive, target_version)
    target_version = versionutils.convert_version_to_tuple(target_version)
    for (version, remove_fields) in added_fields:
        if (target_version < version):
            for obj_field in remove_fields:
                primitive.pop(obj_field, None)
