Sorting objectClass and krb5Key module

[tridge at samba.org]

Andrew,

 > My feeling was that as I was going to do a modify at this particular
 > point in the stack, that I should obtain the data at the same point.  

If you think thats essential, then we could have a
ldb_next_request_talloc() call that copies the request structure so as
to ensure the following modules get a talloc ptr. I wouldn't want
ldb_next_request() to do that every time (as it would be too slow) but
doing it for situations like this would be fine.

 > Yep.  That's all we actually sort on.

ok, then I think we should aim to make the "level" of an objectclass
easily available.

Cheers, Tridge