cta/CTA#144 Don't forget to replace temporary fix for XrdCtaFile::xCom_deletearchive()

This commit does two things.  Firstly it puts back the call from:

    XrdCtaFile::xCom_deletearchive()

to:

    Scheduler::deleteArchive()

Secondly it moves the reponsibility of logging the
"Archive File Deleted" message from the CTA front-end (XrdCtaFile)
to the CTA catalogue.

Please note that Scheduler::deleteArchive() still does not call
SchedulerDatabase::deleteArchiveRequest().