Fixed archive queue not being deleted on last archive job pop.
Next step is retrieve mount scheduling.

Added the retryable error exception and added the catching of different backend exceptions in the frontend

Implementation of the top level retrieve request queueing in Scheduler.

Added the new disk instance field for storage class, requester, requester group, archive route to the frontend

Added comments to scheduler functions to specify the possible exceptions that EOS commands should receive in case of user errors

This reverts commit d2785a95.

This reverts commit 4b1ddfc7.