Replace update.sh functionality

Currently we internally use a couple shell scripts to parse arguments and make sure a copy of ```ceph-qa-suite``` are checkout out before we run ```teuthology-suite```. That always seemed brittle and, more importantly, not fair to the community since those tools were kept out-of-tree. This PR adds the same functionality to teuthology itself.
I use an assert because I'd rather not blindly remove things if they might not belong to these tests.

I also don't think cleaning up is really a "problem". It seems to be working just fine.