Save or update the cluster to persistent state.

        :param cluster: cluster to save or update
        :type cluster: :py:class:`elasticluster.cluster.Cluster`

def save_or_update(self, cluster):
        """Save or update the cluster to persistent state.

        :param cluster: cluster to save or update
        :type cluster: :py:class:`elasticluster.cluster.Cluster`
        """
        if not os.path.exists(self.storage_path):
            os.makedirs(self.storage_path)

        path = self._get_cluster_storage_path(cluster.name)
        cluster.storage_file = path
        with open(path, 'wb') as storage:
            self.dump(cluster, storage)