Update MetalTest for constant scoping change in 1.9

actionpack/test/controller/new_base/metal_test.rb

@@ -20,8 +20,8 @@ def call(env)
   class TestMiddleware < ActiveSupport::TestCase
     def setup
       @app = Rack::Builder.new do
-        use MetalMiddleware
-        run Endpoint.new
+        use MetalTest::MetalMiddleware
+        run MetalTest::Endpoint.new
       end.to_app
     end