Print CTA_BUILD_ID in the jobs and not the full SHA of the commit of course. The generated rpm version was OK but the logs were useless.

`CI_BUILD_REF` environment variable has been dropped in [gitlab 9.0](https://cern.service-now.com/service-portal/view-outage.do?n=OTG0037271)

Fixed.

Removed the dependency between cta-cli and the xrootd
"meta package".

Lambdas were stored on stack and passed to async. They are now stored in object with proper lifetime.
Improved ArchiveMount::getNextJobBatch(): we now clean up the empty queues.

BackendVFS now throws the same exceptions as BackendRados.
The exceptions of the user provided update callback are now passed through.
A unit test was added.

This reverts commit 22685812.

Added comment to cta_catalogue_db.conf.example that explains which connection string should be used when

Added an intermediate interface to reuse SchedulerDatabaseFactory.
Added optional debug infos for BackendVFS constructor.
The unit test is currently disabled.

The ArchiveJobs are now updated using asynchronous IO.

When dropping the database schema, tables and sequences are only
dropped if they are present.

This commit avoids the message "table or view does not exist" by
modifying cta-catalogue-schema-drop to simply not try to delete
tables that do not exist.

cta/CTA#87 cta-catalogue-delete-all-data and cta-catalogue-schema-drop should require interactive confirmation

Removed the now redundant locking commands for the catalogue schema.
These commands were made redundant when the cta-catalogue-schema-drop
command was made interactive.

The VFS implementation only launches the operation in the background (via std::async).
The Rados implementation uses the aio features of Rados. Lock and update are launched in the background via std::async.
Also now uses override for Backend virtual function.

cta/CTA#87 cta-catalogue-delete-all-data and cta-catalogue-schema-drop should require interactive confirmation

Made the cta-catalogue-schema-drop command interactive

xrootd.spec.in in the XRootD SSI branch does not package the SSI
libraries/headers. I'm putting a patched version here temporarily until
Michal or Andy can fix it in the main XRootD repository.

Done.