Removed another couple of redundant tests

The event_based_bcr calculator is tested much better in qa_tests/risk/event_based_bcr. The unittest here is redundant and also annoying, because it counts the number of outputs and when it changes (on purpose) it breaks. Let us have a single test to fix and not two. Idem for classical_bcr.

See https://bugs.launchpad.net/oq-engine/+bug/1372833.