Fix privacy issue with default xrootd monitoring/reporting config

The default monitoring/reporting configuration recommended so far by LHC experiments and used in Quattor had a privacy issue (user DN reported). This modification implements the recommended changes, see:
* https://twiki.cern.ch/twiki/bin/view/AtlasComputing/FAXproxyNew#Xrootd_configuration
* https://svnweb.cern.ch/trac/lcgdm/wiki/Dpm/Xroot/Setup#ATLASmonitoringonly