Corrected helgrind errors by adding mutexes for multithread access to RecallReportPacker attributes.

If the disk threads are not finished after the TapeReadSingleThread finished, the status of the drive will be "DrainingToDisk"
This removed a RecallReportPacker exception when trying to release disk space reservation for backpressure

In DriveState::addDiskSpaceReservation and substractDiskSpaceReservation, use a reference to the mutable_disk_space_reservations item

Added UNIQUE constraint on STORAGE_CLASS_NAME and removed the the UNIQUE constraint on DISK_INSTANCE_NAME and STORAGE_CLASS_NAME

Revert "Scheduler getNextMount() does not return an ArchiveForRepack mount on a tape that is being repacked."

This reverts commit d6f97e34.

Scheduler getNextMount() does not return an ArchiveForRepack mount on a tape that is being repacked.

Scenario:
The operator launches a Repack Request in a tape V01001 (full)
During the expansion, he sets the full flag to false. The tape could be mounted for Archival. Worse, the tape could repack in itself !
This is not possible anymore.

If Repack --disabledtape Retrieve jobs are in the queue, the Retrieve mount will be triggered and the user retrieve jobs will be popped as well as the Repack Retrieve jobs

This is so that the exception will be handled correctly by cta-admin
when an invalid vid is specified to "cta-admin repack"

Corrected the segmentation fault problem if exception happens while the reporting of ArchiveSuccesses fails

Set the status as RJS_Failed of Retrieve Failed jobs after report success before being queued in the RetrieveQueueFailed

Retry queueing in ArchiveQueueToReportToRepackForSuccess if switchElementsOwnership fails because of a rados::lockbackoff() problem

Added repack ls command at repack failure in repack system test

Corrected scheduling to wait for more files to be queued before creating ArchiveForRepack mount + Unit test

Disk reservation where cleaned up in states when they should be kept.
Added disk reservation logs.

Added files and bytes count for Retrieved files from User or Repack in the "tape session finished" message
Made the Repack system test clearer by printing steps and by adding folders for the reports

Changed the logging of successful Retrieve and Archive jobs to differentiate between User and Repack jobs

Added activable logs to the RetrieveQueueStatistics cache for debugging

Added a check for the repack just add copies workflow that verify that two archive routes does not point to the same tapepool

Remove the repack buffer if the repack expansion indicates that no Retrieve is necessary
Corrected the XrootDirectory::exist() method

Wrong parameter was passed as retrieve request id.
Added logs to frontend.
Implemented validation of cancel in archive retrive test (no file should be retrieved).

Also improved function name to better match XRootd names.

The retrieve request address is now stored in the EOS namespace as an extended attribute and deleted
after checks on cancellation. The cleanup of the queues will be eventually done by the tape servers.