ActiveStorage jobs are now moved to their own queue.
For consistency, we also move our own analysis jobs (VirusScannerJob)
on the same `:active_storage_analysis` queue.
We currently have many failed VirusScannerJob enqueued, because the
underlying blob is missing.
This PR fixes the issue by discarding the job in those cases (because if
the blob is gone, the job is never going to succeed).
The implementation is based on a similar issue encoutered by the
ActiveStorage::AnalyzeJob. See 06f8baf73c