I saw your message on the website http://lists.openstack.org/pipermail/openstack-discuss/2019-April/005635.html . And  i have been troubled by the same problem for a long time . I tried to change the parameters resume_guests_state_on_host_boot=True and instance_usage_audit=True
in the nova.conf ,but it didn't work . I wonder if you have solved this problem, looking forward your reply, Thank you and best regards.