Comment 1 for bug 1488986

even ignore periodic task update_available_resource, I think there is still race condition for scheduler.
if first boot request uses ---max-count option, saying 10, and the ten instances are scheduled to the same compute node. And the corresponding compute node service will try to spawn the instances one by one. when handling the 3rd one, the compute info in DB has only accounted 3 instances' consumption. At this moment, the second boot request is being handled by scheduler and the HostState for this boot is updated with info from DB which only accounts 3 instances' consumption. So second boot can be scheduled wrongly.