Can confirm that this issue is NOT reproducible on Bionic/Stein, will test on Bionic/Train now.

$ juju config nova-compute-kvm openstack-origin
cloud:bionic-stein
$ juju config nova-compute-kvm libvirt-image-backend
qcow2

$ os server list -f yaml
- Flavor: m1.tiny
  ID: 3612ca0d-0b6b-4104-8663-54d8d891b100
  Image: cirros
  Name: demo
  Networks: internal=10.0.0.115, 172.27.86.146
  Status: ACTIVE

$ os server image create --wait demo -f yaml

checksum: null
container_format: null
created_at: '2020-09-22T15:04:59Z'
disk_format: null
file: /v2/images/ceca0c58-1fbf-47f6-a94c-f81b265e0c20/file
id: ceca0c58-1fbf-47f6-a94c-f81b265e0c20
min_disk: 1
min_ram: 0
name: demo
owner: 9a163a46437c44109e6ec5b10a7a9ed1
properties:
  base_image_ref: 531d4af1-b6bf-40a2-b4d2-162f8a1e7d1d
  boot_roles: Admin,member,reader
  image_type: snapshot
  instance_uuid: 3612ca0d-0b6b-4104-8663-54d8d891b100
  locations: []
  os_hash_algo: null
  os_hash_value: null
  os_hidden: false
  owner_project_name: admin
  owner_user_name: admin
  user_id: 6b88aca2425c4520a55868f57b6201ca
protected: false
schema: /v2/schemas/image
size: null
status: queued
tags: []
updated_at: '2020-09-22T15:04:59Z'
virtual_size: null
visibility: private


ubuntu@node06:~$ dpkg -l | grep nova
ii  nova-api-metadata                      2:19.3.0-0ubuntu1~cloud0                        all          OpenStack Compute - metadata API frontend
ii  nova-common                            2:19.3.0-0ubuntu1~cloud0                        all          OpenStack Compute - common files
ii  nova-compute                           2:19.3.0-0ubuntu1~cloud0                        all          OpenStack Compute - compute node base
ii  nova-compute-kvm                       2:19.3.0-0ubuntu1~cloud0                        all          OpenStack Compute - compute node (KVM)
ii  nova-compute-libvirt                   2:19.3.0-0ubuntu1~cloud0                        all          OpenStack Compute - compute node libvirt support
ii  python3-nova                           2:19.3.0-0ubuntu1~cloud0                        all          OpenStack Compute Python 3 libraries
ii  python3-novaclient                     2:13.0.0-0ubuntu1~cloud0                        all          client library for OpenStack Compute API - 3.x
ubuntu@node06:~$ dpkg -l | grep libvirt
ii  libvirt-clients                        5.0.0-1ubuntu2.6~cloud0                         amd64        Programs for the libvirt library
ii  libvirt-daemon                         5.0.0-1ubuntu2.6~cloud0                         amd64        Virtualization daemon
ii  libvirt-daemon-driver-storage-rbd      5.0.0-1ubuntu2.6~cloud0                         amd64        Virtualization daemon RBD storage driver
ii  libvirt-daemon-system                  5.0.0-1ubuntu2.6~cloud0                         amd64        Libvirt daemon configuration files
ii  libvirt0:amd64                         5.0.0-1ubuntu2.6~cloud0                         amd64        library for interfacing with different virtualization systems
ii  nova-compute-libvirt                   2:19.3.0-0ubuntu1~cloud0                        all          OpenStack Compute - compute node libvirt support
ii  python3-libvirt                        5.0.0-1~cloud0                                  amd64        libvirt Python 3 bindings
ubuntu@node06:~$