It doesn't make sense to make the callback with credentials that the
client made the setclientid with.  Instead the spec requires that the
callback occur with the credentials the client authenticated *to*.
It probably doesn't matter what we use for auth_unix, and some more
infrastructure will be needed for auth_gss, so let's just remove the
cred lookup for now.
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
Acked-by: Neil Brown <neilb@suse.de>