Comment 29 for bug 1583009

Newton->Ocata would be libvirt 1.3.1 (Xenial) -> 2.5 Upgrade (Zesty).

I tried two updates:
1. X-Newton -> X-Ocata
2. Xenial -> Zesty (EOL, so used Artful with 3.6 here)

Test according to commend #28 was:
1. get on X/X-N a guest
2. check status of virtlogd
3. upgrade
4. virsh shutdown/start after upgrade (which is supposed to hang)
5. checking virtlogd service status

The service was still:
  active (running) since Mon 2018-01-29 09:12:42 UTC; 8min ago

But you see on the 8 min ago, it was still "the old service" it was still on the same PID.
But the reload that is supposed to happen was triggered one could see the new entries in the log:
Jan 29 09:21:21 xenial-uca-N-O-upgrade systemd[1]: Reloading Virtual machine log manager.
Jan 29 09:21:21 xenial-uca-N-O-upgrade systemd[1]: Reloaded Virtual machine log manager.
Jan 29 09:21:21 xenial-uca-N-O-upgrade virtlogd[3965]: libvirt version: 2.5.0, package: 3ubuntu5.6~cloud0 (Openstack U
Jan 29 09:21:21 xenial-uca-N-O-upgrade virtlogd[3965]: hostname: xenial-uca-N-O-upgrade.lxd

But not only list, but also stop/start worked just fine.
Something must be different in your case - any suggestion which part of the setup/config might be special in your case?