Prefer the realm of the user when doing referrals style ISC krb5-get-creds

The the realm of the user's principal and prefer that when doing a lookup.
This code still need to be smarter can cache the "initial value" -> positive result
to avoid roundtrips to the KDC.

lib/gssapi/krb5/canonicalize_name.c

@@ -48,7 +48,7 @@ OM_uint32 _gsskrb5_canonicalize_name (
 
     GSSAPI_KRB5_INIT (&context);
 
-    ret = _gsskrb5_canon_name(minor_status, context, 1, input_name, &name);
+    ret = _gsskrb5_canon_name(minor_status, context, 1, NULL, input_name, &name);
     if (ret)
 	return ret;