Further cleanups on QA

This is more of an RFC. The patch attempts to address two issues:

- running conditional tests is ugly right now
- we don't know what tests we skipped

By using the new RunTestIf, we solve both. But a significant number of
test decisions are more complex than just “is test enabled”, so those
remain to be run via RunTest, which means we don't get logging of when
they're not run. Hence the logging is not complete… Sugesstions on how
to solve it are welcome.

Signed-off-by: Iustin Pop <iustin@google.com>
Reviewed-by: René Nussbaumer <rn@google.com>