Make sure that the currently-set language is the one that shows on the left sidebar if no language  preference exists.

Some students were confused by the display on the sidebar when it would say 'English' even if the text was in another language. This should fix the problem.

@flowerhack @sarina @stephensanchez 

ECOM-135
Unfortunately, this method is extremely difficult to test and so I don't think it's worth the effort to do it, especially while we plan the refactor of all this code in Q2.