Sort of. It already knew.
We have a mess where new things get sent to the server as
KRB5_TL_EXTENSION, but old things get sent to the client as whatever
appropriate KRB5_TL we have, and... we call perform_tl_data() on all TL,
but we don't remove unmodified TL on the client side, and...
Anyways. This commit is a band-aid, but it works.