r23225: Attached find a patch that makes use of NetSamLogonEx in

r23225: Attached find a patch that makes use of NetSamLogonEx in
winbind. With this and W2k3 DCs around it is possible to use
more than one winbind on the same machine account, because
NetSamLogonEx does not use the credentials chain.

I added the flag domain->can_do_samlogon_ex because this
only works against W2k3 and with schannel. The theory is to
try if we're AD and have schannel, and fall back to
NetSamLogon if this fails. can_do_samlogon_ex is thus a
protection against multiple failures.

Only checking into 3_0, this needs more review before going
into a production release.

Feel free to comment :-)
(This used to be commit f5d525399b0b03a3d0b223fe72ef0a8a631fc599)