Use keytab to select etypes in krb5_get_init_creds_keytab()

[Greg Hudson]

On 04/17/2012 02:39 PM, Nico Williams wrote:
> Would that be a problem?  I'm inclined to think that it would be.  But
> I'm not sure.  After all, it's only a "default".  Perhaps the right
> answer is "that's OK, but don't allow any non-permitted_enctypes",
[...]
> Is it time to have an enctype_preference parameter listing enctypes in
> order of preference?

I don't see any advantages to these alternatives over using
default_tkt_enctypes as a preference order (for this particular bit of
code).