[PATCH 2/2] pass the verto_ctx into preauth plugins

[Sam Hartman]

I wonder whether providing the verto context as part of the KDC rock
would be a better idea.  I think we definitely want to avoid a
dependency on the kernel lib on verto.  I also think that since most
preauth plugins and most entry points do not need a verto context it
should come from the rock if needed.

Regardless, I think the krb5_context should come before the
verto_context.