code: void alreadyCompletedTask(TaskAttemptID taskid) {
      // 'KILL' the task 
      completedTask(taskid, TaskStatus.State.KILLED);
      
      // Note the reason for the task being 'KILLED'
      addDiagnosticInfo(taskid, "Already completed TIP");
      
      LOG.info("Already complete TIP " + getTIPId() + 
               " has completed task " + taskid);
    }
docs: Indicate that one of the taskids in this already-completed
  TaskInProgress has successfully completed; hence we mark this
  taskid as {@link TaskStatus.State.KILLED}.