@AfterClass
  public static void tearDownAfterClass() throws Exception {
    TEST_UTIL.shutdownMiniCluster();
  }
This class is for testing HBaseConnectionManager ServerBusyException. Be careful adding to this
class. It sets a low HBASE_CLIENT_PERSERVER_REQUESTS_THRESHOLD
hbase-server/src/test/java/org/apache/hadoop/hbase/client/TestServerBusyException.java