@Override
  public boolean addDependentTask(Task<?> dependent) {
    boolean ret = false;
    if (getListTasks() != null) {
      ret = true;
      for (Task<?> tsk : getListTasks()) {
        ret = ret & tsk.addDependentTask(dependent);
      }
    }
    return ret;
  }
Add a dependent task on the current conditional task. The task will not be a direct child of
conditional task. Actually it will be added as child task of associated tasks.

@return true if the task got added false if it already existed
ql/src/java/org/apache/hadoop/hive/ql/exec/ConditionalTask.java