BZ #1151176 -  fence_xvm: expose port param, add firewall rule

https://bugzilla.redhat.com/show_bug.cgi?id=1151176

port param is a vm name or uuid.
Merge pull request #373 from cwolferh/xvm_tweaks

BZ #1151176 - fence_xvm: expose port param, remove unused params, add firewall rule