We have some cross-realm principals in an MIT KDB with one kind of
1DES enctype, but the other realm's KDCs issue x-realm TGTs where
the ticket encpart key enctype is a different 1DES enctype. We need
this to work if we use Heimdal with the MIT HDB backend.
An alternative would be to check for similar (or, rather,
compatible) enctypes in the KDC (and elsewhere?). This patch avoids
the need to make such ugly changes elsewhere.