r2041: Fix NTLMSSP RPC sealing, client -> win2k3 server.

r2041: Fix NTLMSSP RPC sealing, client -> win2k3 server.

The bug (found by tridge) is that Win2k3 is being tighter about the
NTLMSSP flags.  If we don't negotiate sealing, we can't use it.

We now have a way to indicate to the GENSEC implementation mechanisms
what things we want for a connection.

Andrew Bartlett
(This used to be commit 86f61568ea44c5719f9b583beeeefb12e0c26f4c)