send something to upstream about the GSSAPIKeyExchange missing keytab problem

[geofft]

We locally fixed #315 by hacking on the initscript. There are some somewhat-more-upstreamable solutions proposed in my comment involving hacking the source instead; we should report this upstream and preferably send them a patch to do one of those solutions.

I think a server-side fix is preferable to a client-side fix.

[geofft]

This is a little more general than just a missing remote keytab, by the way; I ran into this and briefly got highly confused wen I had local clock skew.

[ghudson]

It's conceivable that this is fixed in krb5 1.11, since gss_acquire_cred for gss-krb5 acceptor credentials will fail immediately if the keytab doesn't exist.

[andersk]

For the record, this is still a problem in Ubuntu 16.04 (krb5 1.13.2+dfsg-5, openssh-server 7.2p2-4ubuntu1). However, we removed the workaround of #315 because we now expect clients not to have GSSAPIKeyExchange on (#1386), and because the workaround broke ssh under systemd (#1562).