[xenserver] add missing Host attributes (edition, software_version)

lib/fog/xenserver/models/compute/host.rb

@@ -23,6 +23,8 @@ module Fog
         attribute :__pifs,            :aliases => :PIFs
         attribute :__resident_vms,      :aliases => :resident_VMs
         attribute :__host_cpus,         :aliases => :host_CPUs
+        attribute :edition
+        attribute :software_version
         
         def pifs
           __pifs.collect { |pif| service.pifs.get pif }

tests/xenserver/models/compute/host_tests.rb

@@ -28,7 +28,9 @@ Shindo.tests('Fog::Compute[:xenserver] | host model', ['xenserver']) do
         :__pbds,
         :__pifs,
         :__resident_vms,
-        :__host_cpus
+        :__host_cpus,
+        :edition,
+        :software_version
       ]
       tests("The host model should respond to") do
         attributes.each do |attribute|