This storage class is ignored during CREATE, so that we don't need to
set up an archive route just for testing.

This decouples the "cta-admin tf ls" command from looking up path names
in the catalogue, paving the way to remove the path from the DB.

The catalogue.ping() method now checks the equality between the MAJOR version number of the CTA schema version and the MAJOR version number in the database

1. Needs to be sys.* so users can't change it
2. Should not be confused with sys.retrieve.req_id

Renames CTA_ArchiveFileID to sys.archive.file_id
Renames CTA_StorageClass to sys.archive.storage.class

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.

Google protobuf3 logs a FATAL error if .at() is called for a
non-existent key, so the log is filled with errors if we use try {}
catch(...) {}

kill. This is quite likely for cta-taped as its static memory buffer
consume a lot of memory.

The sleep time (15 minutes) is currently hardcoded, but implemented in a single place (OStoreDB::fetchMountInfo() ).