s3-lsa: let _lsa_GetSystemAccessAccount() call into _lsa_EnumPrivsAccount().

s3-lsa: let _lsa_GetSystemAccessAccount() call into _lsa_EnumPrivsAccount().

Inspired by lsa server from Samba 4.

Just removing a user in SAMR does not remove a user in LSA. If you use
usermanager from windows, the "User Rights" management gui gets unaccessable as
soon as you delete a user that had privileges granted. With this fix, that
no longer existing user would properly appear as an unknown account in the GUI
(as it does while using usermanager with windows domains).

This almost makes Samba3 pass the RPC-SAMR-USERS-PRIVILEGES test.

Guenther