[sepia] Brief build outage to switch in upgraded shaman

I plan to switch in the upgraded shaman this weekend, because past experience shows builds slow regularly on Friday/Saturday. (It is currently running on a very old version of Ubuntu with a very old version of Postgres and a very old version of Python; we've resolved all that.) It will involve a shutdown of the existing shaman servers to 1) snapshot and populate the new server's database, and 2) change the IP of the server to the existing 1.shaman.ceph.com IP I've run through this process a few times in isolation, and I expect it to take no more than 10-15 minutes. I'll announce when it's imminent, either later this evening or tomorrow.