[sepia] Jenkins shutdown for maintenance

I'm going to start the shutdown procedure for Jenkins to drain jobs in preparation for maintenance this evening (Friday 14 Jun), probably around 1800 PDT (so 0100 Saturday 15 Jun UTC). I intend to do a clean shutdown, so jobs should not be canceled, just delayed. I hope to have jenkins back up in roughly an hour once the queue drains; it's difficult to predict how long that will be, but expect a downtime of 3-4 hours, anyway. I'll notify here when it's back.