Check for keys in encrypted timestamp/challenge

Encrypted timestamp and encrypted challenge cannot succeed if the
client has no long-term key matching the request enctypes, so do not
offer them in that case.

https://github.com/krb5/krb5/commit/9593d1311fa5e6e841c429653ad35a63d17c2fdd
Author: Greg Hudson <ghudson@mit.edu>
Commit: 9593d1311fa5e6e841c429653ad35a63d17c2fdd
Branch: master
 src/kdc/kdc_preauth_ec.c    |    7 ++++++-
 src/kdc/kdc_preauth_encts.c |    6 +++++-
 2 files changed, 11 insertions(+), 2 deletions(-)