Revert "Modified internal_filename handling in job reports."

This reverts commit b422cee2f80496a13e40da8719128ceb8d5a9cb9.
Revert "Added support for internal report metadata."

This reverts commit 13c4970ec688f3534ae297918c399a5e51878505.
JobManager: Generate internal filename in store_report instead of using the one given as parameter.
Delete internal attribute when returning report metadata.
Fixed bug: internal_filename not stored in job report metadata.