dont redefine classmethod on initialize

Signed-off-by: Dominik Richter <dominik.richter@gmail.com>

lib/vulcano/plugins/resource.rb

@@ -13,10 +13,14 @@ module Vulcano
           include Vulcano::Plugins::ResourceCommon
           def initialize(backend, *args)
             # attach the backend to this instance
-            self.class.send(:define_method, :vulcano) { backend }
+            @__backend_runner__ = backend
             # call the resource initializer
             super(*args)
           end
+
+          def vulcano
+            @__backend_runner__
+          end
         end
 
         # add the resource to the registry by name