OCI: Attempt to fix "runtime" container

Chase the kerberos -> krb5 change in pkgbase packages.

We don't currently have any way of making this conditional on the
WITH_MITKRB5 variable, so we're going based on the default value.
On the other hand, that's also true of other WITH_* variables too.

This change might get backed out shortly; discussions are underway
about whether MIT Kerberos 5 should be "krb5" or simply "kerberos".

With hat: re (unbreaking weekly snapshot builds)
Co-authored-by: dch
Differential Revision: https://reviews.freebsd.org/D51481