add ipv6_only support to blue box

lib/fog/bluebox/models/compute/server.rb

@@ -21,6 +21,7 @@ module Fog
         attribute :state,       :aliases => "status"
         attribute :storage
         attribute :template
+        attribute :ipv6_only
 
         attr_accessor :hostname, :password, :lb_applications, :lb_services, :lb_backends
 
@@ -91,6 +92,7 @@ module Fog
 
           options['username'] = username
           options['hostname'] = hostname if @hostname
+          options['ipv6_only'] = ipv6_only if @ipv6_only
           data = service.create_block(flavor_id, image_id, location_id, options)
           merge_attributes(data.body)
           true