r12903: Factor out a new routine libnet_RpcConnectDCInfo, to both connect to

r12903: Factor out a new routine libnet_RpcConnectDCInfo, to both connect to
the remote sever, and to query it for domain information.

Provide and use this information in the SamSync/Vampire callbacks, to allow a
parallel connection to LDAP, if we are talking to AD.  This allows us
to get at some important attributes not exposed in the old protocol.

With this, we are able to do a all-GUI vampire of a AD domain from
SWAT, including getting all the SIDs, servicePrincipalNames and the
like correct.

Andrew Bartlett
(This used to be commit 918358cee0b4a1b2c9bc9e68d9d53428a634281e)