r23530: Fix bugs #4678 and #4697 which had the same root cause.

r23530: Fix bugs #4678 and #4697 which had the same root cause.
In make_server_info_pw() we assign a user SID in our
authoritative SAM, even though this may be from a
pure "Unix User" that doesn't exist in the SAM.
This causes lookups on "[in]valid users" to fail as they
will lookup this name as a "Unix User" SID to check against
the user token. Fix this by adding the "Unix User"\unix_username
SID to the sid array. The correct fix should probably be
changing the server_info->sam_account user SID to be a
S-1-22 Unix SID, but this might break old configs where
plaintext passwords were used with no SAM backend.
Jeremy