Merge from 3.0:

Merge from 3.0:

Add support for variable-length session keys in our client code.

This means that we now support 'net rpc join' with KRB5 (des based)
logins.  Now, you need to hack 'net' to do that, but the principal is
important...

When we add kerberos to 'net rpc', it should be possible to still do
user management and the like over RPC.

-

Add server-side support for variable-length session keys (as used by
DES based krb5 logins).

Andrew Bartlett
(This used to be commit 1287cf5f921327c9ea758de46220c4e2dedc485c)