Give api server operation tracking ability

Pending and recently completed operations now served at: /api/v1beta1/operations/id#

Handling of async operations is now consistent and sensible (ish). We check for admissibility before starting a long wait. I added some ID != "" checks here, but probably more things should be checked.
Doing it this way lets me wait for both notify and a timeout in WaitFor()... sync.Cond doesn't appear to have a WaitFor method. Also, I find this much easier understand than sync.Cond, but YMMV on that.