It is possible for more than one vCPUs to trigger shutdown on an RTVM.
We need to avoid entering VM_READY_TO_POWEROFF state again after the
RTVM has been paused or shut down.
Also, make sure an RTVM enters VM_READY_TO_POWEROFF state before it can
be paused.
v1 -> v2:
- rename to poweroff_if_rt_vm for better clarity
Tracked-On: #5411
Signed-off-by: Peter Fang <peter.fang@intel.com>
68dc8d9f8f