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.
The concern really is if you are expecting the user to be almost always something like `ubuntu` and not `root`.
If `src` is a directory that is always going to be present regardless of `root` or `ubuntu` (or something else) then all is good