public String waitOnRegionServer(int serverNumber) {
    JVMClusterUtil.RegionServerThread regionServerThread = this.regionThreads.get(serverNumber);
    return waitOnRegionServer(regionServerThread);
  }
Wait for the specified region server to stop. Removes this thread from list of running threads.
@return Name of region server that just went down.
hbase-server/src/main/java/org/apache/hadoop/hbase/LocalHBaseCluster.java