Sidekiq retries jobs that ActiveJob was instructed to discard

[CristinaRO]

What happens:

• the bulk user import fails because an InvalidSalesforceID exception is raised;
• the ensure block deletes the uploaded file from the bucket;
• Sidekiq (not ActiveJob!) retries the failed job anyway, because Sidekiq doesn't respect or acknowledge the discard_on instruction; that's an ActiveJob thing, too lowly for Sidekiq to bother with;
• the job fails because the file is not there;
• a baffling error appears in Rollbar.

Possible fix: instruct Sidekiq to not retry at all, by configuring sidekiq_options, and rely on ActiveJob's approach.