[krbdev.mit.edu #7945] -r option to krb5kdc does not work

[Andrea Campi via RT]

The check for the return value of find_realm_data at
https://github.com/krb5/krb5/blob/master/src/kdc/main.c#L691 is reversed,
with the result that no valid realm with ever pass validation. Worse, it
will be silently ignored, only to fail later when looking for the master
key.

This has been there since 1995 :D

https://github.com/krb5/krb5/commit/36b0618997fd316a4f8fff8878c12e30839606a6