yum::repo::epel: hardcode CentOS version for XenServer.
yum: hardcode CentOS version for XenServer.
yum::repo::puppetlabs: hardcode osver for XenServer.
Add XenServer repositories management.
Enable XenServer repo configuration.
yum::repo::xenserver: do not enable centosplus and extras repos by default.
Merge pull request #69 from gnubila-france/xenserver_support

Add XenServer support