Add regression test for LDAP key fencepost bug

(cherry picked from commit 0d78da225612e13d0b1cf515987305535d2f9dce)

https://github.com/krb5/krb5/commit/78a7f2a02b82bf297817cd717f092ead40b575b2
Author: Greg Hudson <ghudson@mit.edu>
Committer: Tom Yu <tlyu@mit.edu>
Commit: 78a7f2a02b82bf297817cd717f092ead40b575b2
Branch: krb5-1.12
 src/tests/t_kdb.py |   11 +++++++++++
 1 files changed, 11 insertions(+), 0 deletions(-)