Download gru is attached to all scheduled jobs when doing 'isos post'
Create one test suite with 'HDD_1_URL=xxx' and add it to a job group, when doing 'isos post' to trigger the job group's jobs, all jobs are blocked by this download gru task.
AC: The download gru task only blocks its related job.
Seems like we need to track the list of relevant job IDs individually for each download. Sorry that I've overlooked that "detail" when suggesting the approach - but I guess it shouldn't be too hard to extend it as we already track multiple destinations per download.