'Update metadata items for specific volume
http://localhost/api/cinder/volumes/1/metadata'

@rest_utils.ajax()
def patch(self, request, volume_id):

    updated = request.DATA['updated']
    removed = request.DATA['removed']
    if updated:
        api.cinder.volume_set_metadata(request, volume_id, updated)
    if removed:
        api.cinder.volume_delete_metadata(request, volume_id, removed)
