private void waitUntilRegionServerDead() throws InterruptedException, IOException {
    // Wait until the master processes the RS shutdown
    for (int i =
      0; (cluster.getMaster().getClusterMetrics().getLiveServerMetrics().size() > NB_SERVERS
        || cluster.getLiveRegionServerThreads().size() > NB_SERVERS) && i < 100; i++) {
      LOG.info("Waiting on server to go down");
      Thread.sleep(100);
    }
    assertFalse("Waited too long for RS to die",
      cluster.getMaster().getClusterMetrics().getLiveServerMetrics().size() > NB_SERVERS
        || cluster.getLiveRegionServerThreads().size() > NB_SERVERS);
  }
Find regionserver other than the one passed. Can't rely on indexes into list of regionservers
since crashed servers occupy an index.
@return A regionserver that is not <code>notThisOne</code> or null if none found
hbase-server/src/test/java/org/apache/hadoop/hbase/regionserver/TestSplitTransactionOnCluster.java