dsdb-acl: Do not apply ACL on special DNs to hide attributes that the user shouldn...

dsdb-acl: Do not apply ACL on special DNs to hide attributes that the user shouldn't see

This fix frequent reindexing when using python script with a
user that is not system.
The reindexing is caused by ACL module hidding (removing) attributes in
the search request for all attributes in dn=@ATTRIBUTES and because
dsdb_schema_set_indices_and_attributes checks that the list of
attributes that it just calculated from the schema is the same as the
list written in @ATTRIBUTES, if not the list is replaced and a
reindexing is triggered.

Signed-off-by: Matthieu Patou <mat@matws.net>
Reviewed-by: Stefan Metzmacher <metze@samba.org>