[Cryptech Core] Server maintenance

[Rob Austein]

Shutting down all VMs in Cryptech Reykjavik cluster briefly to update
kernel in underlying physical hardware.

Longer term, we're going to need to schedule a longer maintenance
window at some point, because the release that same physical hardware
is running is getting kind of long in the tooth.  But we'll want to
snapshot the VMs before doing that, etc, so it won't be today.