*: generate clusterid

Generate clusterID based on hash(sorted(MemberIDs), discoveryURL)
@jonboulle We decided to generate NodeID with clusterName -> nodeID = hash(peerurls, clusterName)
clusterID = hash(sorted IDs). when we decide to generate nodeID = hash(peerurls, clusterName. discoveryURL), we can remove the clusterID generation salt.