private void runNIsMoreThanOne(final Class<? extends Test> cmd)
    throws IOException, InterruptedException, ClassNotFoundException {
    RemoteAdmin remoteAdmin = new RemoteAdmin(new Client(cluster), getConf());
    checkTable(remoteAdmin);
    if (nomapred) {
      doMultipleClients(cmd);
    } else {
      doMapReduce(cmd);
    }
  }
We're to run multiple clients concurrently. Setup a mapreduce job. Run one map per client. Then
run a single reduce to sum the elapsed times.
@param cmd Command to run.
hbase-rest/src/test/java/org/apache/hadoop/hbase/rest/PerformanceEvaluation.java