code: public void forceClean() {
      while(true) {
        PathDeletionContext context = null;
        try {
          context = cleanupThread.queue.poll(50L, TimeUnit.MILLISECONDS);
          if (context == null) {
            return;
          }
          if (!deletePath(context)) {
            LOG.warn("forceClean:Unable to delete path " + context.fullPath);
          }
          else {
            LOG.info("foceClean DELETED " + context.fullPath);
          }
          
        } catch (InterruptedException e) {
          return;
        } catch (Exception e) {
          LOG.warn("Error deleting path " + context.fullPath + ": " + e);
        } 
      }
    }
docs: Force to clean the all path, it should be called when task tracker is shut down
  Now we only called it in MiniCoronaCluster to make sure the unit test run in a clean
  fixture