If a user has a portfolio role, do not filter patient data to a single measure on HTML export

I've changed the patients controller so that if a user has a portfolio role, an empty list is passed to the html exporter. A new test user (user_portfolio) is used to test that this works.

Currently, my test looks for the presence of an element with the narr_table class. Test records do not contain any entries associated with CMS138v2 so this table is not present in the output if the user is not a portfolio user.