I can't imagine us *not* having a py3 proxy server at some point, and
that proxy server is going to need a ring.
While we're at it (and since they were so close anyway), port
* cli/ringbuilder.py and
* common/linkat.py
* common/daemon.py
Change-Id: Iec8d97e0ce925614a86b516c4c6ed82809d0ba9b