[openQA] qemu-system-riscv64 设置选项-no-shutdown 无效

[lvxiaoqian555]

根据https://qemu-project.gitlab.io/qemu/interop/qemu-qmp-ref.html#qapidoc-100 中
If the command-line option “-no-shutdown” has been specified, qemu will not exit, and a STOP event will eventually follow the SHUTDOWN event
如果使用-no-shutdown qemu状态应该为shutdown

• guest is shut down (and -no-shutdown is in use)

但是实际使用了-no-shutdown 选项，poweroff以后qemu会退出
对比qemu-system-x86_64，使用-no-shutdown 选项，poweroff以后qemu不会退出