Ticket #18175 Wrong operatingsystem reported for Xen Cloud Platform

Facter will now return XCP for the fact operatingsystem when
/etc/redhat-release contains the XCP version string.
Merge branch 'jaredcurtis-ticket/master/18175_operatingsystem_detect_XCP'

* jaredcurtis-ticket/master/18175_operatingsystem_detect_XCP:
  Ticket #18175 Wrong operatingsystem reported for Xen Cloud Platform

closes #422