Code review comment for lp:~soren/nova/skip-timing-sensitive-tests

I've fixed ratelimiting in general to not unit test using `time.sleep` anymore. IMO testing with `time.sleep` is a hack and I'd rather see it go away than have this go in. :)

I'll not 'Disapprove' because it would be a bias review based on my branch, but feel free to look over my Limits reworking which improves testability and ensures tests are MUCH faster due to no more sleeps. :)

https://code.launchpad.net/~blamar/nova/lp728587/+merge/53554