update global redirector testfile url
CMS AAA migrated to the new set of global redirectors behind DNS alias cms-xrd-global.cern.ch and so changed the way of accessing test file on the hosts behind the DNS alias.
CMS AAA migrated to the new set of global redirectors behind DNS alias cms-xrd-global.cern.ch and so changed the way of accessing test file on the hosts behind the DNS alias.