auth: consistent handling of well-known alias as primary gid

auth: consistent handling of well-known alias as primary gid

When a local user has its primary group id mapped to a well-known
alias or a builtin group, smbd accepts logins of such a user, but
fails tree-connects to shares with a "force user" set to this user
with an error of NT_STATUS_INVALID_SID.

This fix causes the connect to succeed and the NT token to resemble
the token that would have been created in a login.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=11608

Signed-off-by: Uri Simchoni <uri@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>