@Override
    protected Procedure<MasterProcedureEnv>[] execute(MasterProcedureEnv env)
      throws ProcedureYieldException, ProcedureSuspendedException, InterruptedException {
      ARRIVE.countDown();
      RESUME.await();
      return null;
    }
Confirm that we will do backoff when retrying on closing a region, to avoid consuming all the
CPUs.
hbase-server/src/test/java/org/apache/hadoop/hbase/master/assignment/TestCloseRegionWhileRSCrash.java