fix issue where the view handler when enabling the jsonp support would not be public

attempt at fixing https://github.com/FriendsOfSymfony/FOSRestBundle/pull/266#issuecomment-22699781

@stof can you give me a hint here?
i didnt manage to reproduce the issue but it can be because of various examples I have that might for some reason change the default behavior. I can however see how things might be wrong without this change.