qa_tests/risk:

Fixed the base risk QA test case class so that nose attributes work
properly. The involved simply renaming `run_tests` to `_run_tests`.

Without this fix, all of the risk QA tests are run even is you specify
`nosetests -a '!qa'`.
Merge pull request #995 from larsbutler/risk-qa-attr-fix

Fix for Risk QA test collection

[r=micheles]