Run file.close before unlinking for travis

This works on OSX but for some reason travis is throwing a
```
  1) Error:
ExpiresInRenderTest#test_dynamic_render_with_absolute_path:
NoMethodError: undefined method `unlink' for nil:NilClass
```
Looking at other tests in Railties the file has a name and we close
it before unlinking, so I'm going to try that.

actionpack/test/controller/render_test.rb

@@ -301,13 +301,14 @@ def test_dynamic_render_with_file
   end
 
   def test_dynamic_render_with_absolute_path
-    file = Tempfile.new
+    file = Tempfile.new('name')
     file.write "secrets!"
     file.flush
     assert_raises ActionView::MissingTemplate do
       response = get :dynamic_render, { id: file.path }
     end
   ensure
+    file.close
     file.unlink
   end