@After
  @Override
  public void tearDown() throws Exception {
    Closeables.close(ASYNC_CONN, true);
    TEST_UTIL.shutdownMiniCluster();
  }
Only used to test stopMaster/stopRegionServer/shutdown methods.
hbase-server/src/test/java/org/apache/hadoop/hbase/client/TestAsyncClusterAdminApi2.java