Add config log messages to start of XrdSsiCtaServiceProvider (#1035)

CTA frontend now logs the following configuration values at startup

* cta.catalogue.numberofconnections
* cta.objectstore.backendpath
* cta.schedulerdb.numberofthreads
* cta.archivefile.max_size_gb
* cta.repack.repack_buffer_url
* cta.ns.config