make @test_throws type mismatch dispatch to Failure handler 

This started as a one line change to close #7051, then I realized Base.Test was not being tested. Seems like a bit of a chicken and an egg problem. I added some tests, but it is still missing for @test_approx_eq, @test_approx_eq_eps, since failure makes an error instead of dispatching to a handler. I will open another issue for discussion.