It looks like with the systemd-ification of meant specifying
KRB5_KTNAME in /etc/sysconfig/dirsrv no longer works; when
I moved the environment variable to /etc/sysconfig/dirsrv-scripts
it started working. This is probably a bug; I'll make sure I
diagnosed this correctly and then file a report.
If dirsrv could add a log message saying something to the effect
of "using Kerberos keytab at ..." that would probably be great :-)