@Before
  @Override
  public void setUp() throws Exception {
    TEST_UTIL.startMiniCluster(3);
    ASYNC_CONN = ConnectionFactory.createAsyncConnection(TEST_UTIL.getConfiguration()).get();
    admin = ASYNC_CONN.getAdmin();
  }
Only used to test stopMaster/stopRegionServer/shutdown methods.
hbase-server/src/test/java/org/apache/hadoop/hbase/client/TestAsyncClusterAdminApi2.java