@AfterClass
  public static void tearDown() throws Exception {
    if (EVENT_LOOP_GROUP != null) {
      EVENT_LOOP_GROUP.shutdownGracefully().get();
    }
    shutdownMiniDFSCluster();
  }
Make sure lease renewal works. Since it is in a background thread, normal read/write test can not
verify it.
<p>
See HBASE-28955 for more details.
hbase-asyncfs/src/test/java/org/apache/hadoop/hbase/io/asyncfs/TestLeaseRenewal.java