Don't send empty etype info from KDC

RFC 4120 prohibits empty ETYPE-INFO2 sequences (though not ETYPE-INFO
sequences), and our client errors out if it sees an empty sequence of
either.

https://github.com/krb5/krb5/commit/ef700ee2cc1b33a06cd1e5c6c56ca7cfac8e67c5
Author: Greg Hudson <ghudson@mit.edu>
Commit: ef700ee2cc1b33a06cd1e5c6c56ca7cfac8e67c5
Branch: master
 src/kdc/kdc_preauth.c |    5 +++++
 1 files changed, 5 insertions(+), 0 deletions(-)