modified smbd/msrpc credential transfer system. user session key

modified smbd/msrpc credential transfer system.  user session key
is *missing* from samba cvs main, therefore it is set to all zeros.
this will cause, amongst other things, administrator-changing-user-passwords,
and setting up new accounts, to fail, as the user's password can only be
decoded with the session key (in this case, the administrator's usr sess key).

it's never a perfect world, is it?
(This used to be commit 3362fcdfa492cfd1d9d4ec35ef2108192302b984)