@RestrictedApi(explanation = "Should only be called in tests", link = "",
      allowedOnPath = ".*/src/test/.*")
  LoadingCache<RegionInfo, HDFSBlocksDistribution> getCache() {
    return cache;
  }
Map hostname to ServerName, The output ServerName list will have the same order as input hosts.
@param hosts the list of hosts
@return ServerName list
hbase-balancer/src/main/java/org/apache/hadoop/hbase/master/balancer/RegionHDFSBlockLocationFinder.java