Copy all the call numbers, not none of them

Sending uninitialized memory over to the peer is unwise, and
also causes it to send us packets that we drop on the floor.

This code is kind of broken anyway (and maybe not compliant with
the latest spec?  I thought we took out the explicit maxcall, but
maybe I'm just thinking of the ncalls).
bosserver: don't hardcode a keytab name

Either put the keys in the system keytab or set KRB5_KTNAME or such.
Do not code bosserver acceptor hostname

Just use gethostname(), as that seems to be most reliable.
bos: respect aencrypt for rxgk

Encrypt when requested, auth otherwise.
(No reason to do clear, really.)