public void startMiniDFS() throws Exception {
    if (testUtil == null) {
      testUtil = new HBaseTestingUtil(conf);
    }
    dfsCluster = testUtil.startMiniDFSCluster(numDataNodes);
  }
Makes this local HBase cluster use a mini-DFS cluster. Must be called before
{@link #startHBase()}.
hbase-diagnostics/src/test/java/org/apache/hadoop/hbase/util/ProcessBasedLocalHBaseCluster.java