Fix failing tests by changing locators

This fixes failures of `test_that_questions_problem_count_increments` and `test_that_questions_sorts_correctly_by_filter_equal_to_unanswered`, but I am still seeing intermittents on `test_contributor_flow_to_support_forum_post`. There is an issue with that test and the markup that I need to discuss with @stephendonner or @rbillings.