libvirt's backup copies the disks of a running or paused VM from one
instant into new volumes while it keeps running; the clone is defined
shut off as before. The VM is held for the copy, the copy can be
cancelled, and recovery reads the job's records and libvirt.
Request jobs (an upload's chunks) run in gunicorn: their kind is admitted
running with the request as its worker, never claimed or recovered by the
worker, cancelled in the request, and asked by every housekeeping pass to
end its jobs that went idle. The panel can follow a job the page just
started. A job a request runs does not wait for the worker, so it does not
raise the worker-unavailable warning on the Jobs page or in the panel.
