rngd isn't running on Linerva

[geofft]

The linerva metapackage depends on rng-tools, whose purpose in life is basically to run the rngd daemon to seed the kernel PRNG with data from a hardware RNG.

The rngd initscript tests for various hardware RNG devices in /dev and /dev/misc, and exits if it can't find one. That seems to be the case on Linerva, at least presently as a VM. (It may not have been the case when Linerva was a physical machine.)

We should either decide it's important and figure out how to get Linerva a proper hardware-randomness device -- and maybe put the dependency in debathena-workstation, or get the official dialups (also VMs) to run it, or something -- or decide it's not important.