Disable GSSAPIKeyExchange

Signed-off-by: Anders Kaseorg <andersk@mit.edu>
Add GlobalKnownHostsFile for athena.dialup and scripts

Signed-off-by: Anders Kaseorg <andersk@mit.edu>
Release debathena-ssh-client-config 1.7

Signed-off-by: Anders Kaseorg <andersk@mit.edu>