When we shutdown/reboot a guest using agent-mode, if the guest itself blocks infinitely,
libvirt would block in qemuAgentShutdown() forever.
Thus, we set a timeout for shutdown/reboot, from our experience, 60 seconds would be fine.
Signed-off-by: NZhang Bo <oscar.zhangbo@huawei.com>
Signed-off-by: NWang Yufei <james.wangyufei@huawei.com>