qemu: Fix type of a completed job
    
    Libvirt 3.7.0 and earlier libvirt reported a migration job as completed
    immediately after QEMU finished sending migration data at which point
    migration was not really complete yet. Commit v3.7.0-29-g3f2d6d829e
    fixed this, but caused a regression in reporting statistics for
    completed jobs which started reporting the job as still running. This
    happened because the completed job statistics including the job status
    are copied from the running job before we finally mark it as completed.
    
    Let's make sure QEMU_DOMAIN_JOB_STATUS_COMPLETED is always set in the
    completed job info even when the job has not finished yet.
    
    https://bugzilla.redhat.com/show_bug.cgi?id=1523036
    
    Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
    Reviewed-by: Pavel Hrdina <phrdina@redhat.com>