public void restartHBaseCluster(int servers) throws IOException, InterruptedException {
    this.restartHBaseCluster(servers, null);
  }
Starts the hbase cluster up again after shutting it down previously in a test. Use this if you
want to keep dfs/zk up and just stop/start hbase.
@param servers number of region servers
hbase-testing-util/src/main/java/org/apache/hadoop/hbase/HBaseTestingUtility.java