tests/krb5: Fix status code checking

The type used to encode the status code is actually KERB-ERROR-DATA,
rather than PA-DATA.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=14642

Signed-off-by: Joseph Sutton <josephsutton@catalyst.net.nz>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>
