s3:auth Make Samba3 use the new common struct auth_usersupplied_info

s3:auth Make Samba3 use the new common struct auth_usersupplied_info

This common structure will make it much easier to produce an auth
module for s3compat that calls Samba4's auth subsystem.

In order the make the link work properly (and not map twice), we mark
both that we did try and map the user, as well as if we changed the
user during the mapping.

Andrew Bartlett