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

release/tools/oci-image-runtime.conf

@@ -12,7 +12,7 @@ oci_image_build() {
 	install_packages ${abi} ${workdir} \
 			 FreeBSD-runtime \
 			 FreeBSD-certctl \
-			 FreeBSD-kerberos-lib \
+			 FreeBSD-krb5-lib \
 			 FreeBSD-libarchive \
 			 FreeBSD-libexecinfo \
 			 FreeBSD-libucl \