Fix the rest server to work with newer cherrypy versions.

Could you please pick this patch for the (new) REST server code? it is needed for running CrabCache, Crabserver, ReqMgr2, SiteDB and T0WMADataSvc on SLC6. This was due to api changes coming from the new cherrypy version we are using in the comp_gcc481 slc6 branch.

I've tested it on VMs and it works for both the new (slc6) cherrypy version and the current (slc5) one we use in production machines.