Revert "389-ds-base: Remove kerberos line as it is strictly dependent on krb5"

This reverts commit b1e4371a1cb5b8aa45ee3cd8b5ba5537f60d53b0.

pkgs/top-level/all-packages.nix

···
 
   ### SERVERS
 
-  "389-ds-base" = callPackage ../servers/ldap/389 { };
+  "389-ds-base" = callPackage ../servers/ldap/389 {
+    kerberos = libkrb5;
+  };
 
   rdf4store = callPackage ../servers/http/4store { };