[vcloud_director] Cater for email@org_name usernames.

lib/fog/vcloud_director/compute.rb

@@ -497,10 +497,12 @@ module Fog
           @org_name ||=
             begin
               username = @vcloud_director_username.split('@')
-              unless username.size == 2
+              if username.size >= 2 # may be 'email_address@org_name'
+                username.last
+              else
                 Fog::Logger.warning('vcloud_director_username should be in the form user@org_name')
+                'vcd_org_name'
               end
-              username.last || 'vcd_org_name'
             end
         end