'Update an existing attachment record.'

@wrap_check_policy
def attachment_update(self, ctxt, attachment_ref, connector):

    volume_ref = objects.Volume.get_by_id(ctxt, attachment_ref.volume_id)
    connection_info = self.volume_rpcapi.attachment_update(ctxt, volume_ref, connector, attachment_ref.id)
    attachment_ref.connection_info = connection_info
    attachment_ref.save()
    return attachment_ref
