Fixes malformed OBJECT_URL in rackspace setup script

download-release service was failing on kubernetes-master in rackspace because it was trying to download the tarball from a URL ending with

  ?temp_url_sig=4f47ae556255a448139df9eb7b5e38123002162eCLOUD_FILES_URLtemp_url_expires=1418328424

this is due to an improperly escaped backslash in the util.sh script, fixed here.