docs: public List<String> findWorkersWorkingOnPlan(Plan plan) throws WorkerDaoException{
      try {
        Stat exists = framework.getCuratorFramework().checkExists().forPath(PLAN_WORKERS_ZK + "/" + plan.getName());
        if (exists == null ){
          return new ArrayList<String>();
        }
        return framework.getCuratorFramework().getChildren().forPath(PLAN_WORKERS_ZK + "/" + plan.getName());
      } catch (Exception e) {
        throw new WorkerDaoException(e);
      }   
    }