when migrate,I unplugged the disk, why can't I force cancel the job task use qmp
Description of problem:
when migrate,I unplugged the disk,the block job will hung,but why can't I force cancel the job task
Steps to reproduce:
1.migrate a guset to another host with non-share disk (iscsi)

2.unplug the disk

3.then force cancel the block job task


but it not work,the cancle handle is not work

![image](/uploads/e01464f45188df92abc1fe15ccd96777/image.png)

![image](/uploads/0b8ebb654eae4feae06e7fa6dba071ea/image.png)