Make sure that there are no remote wals when transit cluster from DA to A

Consider we have two clusters in A and S state, and then we transit A to DA. And later we want to transit DA to A, since the remote cluster is in S, we should be able to do it. But there are some remote wals on the HDFS for the cluster in S state, so we need to wait the remote wals was removed first before transiting the cluster in DA state to A. Need add a check for this.