os: drop SUN-DES-1 authentication

DES isn't considered secure anymore for long time now, more and more platforms
dropping DES from their RPC implementations, and even the one where it came
from (Solaris) disabled it for a decade now. We have much better alternatives
(eg. passing creds via Unix socket for local connections, ssh tunneling,
MIT-MAGIC-COOKIE-1, ...), so it's unlikely anybody still really relying on it.

Therefore, sweep it out.

Signed-off-by: Enrico Weigelt, metux IT consult <info@metux.net>
Part-of: <!1453>