testcases for RecommenderXBlock

I messed things up in the previous PR, and thus I make a new one. I think I should also change cms/djangoapps/contentstore/views/component.py , but I forget how to do it. Do you know how to do that, and could you help me check is there any other thing wrong, @pmitros ?
Why not move the contents of the `set_up_resources` function to here? There's no reason to define it on the `TestRecommender` class if that class never uses it. Then, you can either make `TestRecommenderEvaluationWithResources` inherit from `TestRecommenderCRUDWithResources`, or just pull all of the test functions from those two classes together into one class.