acl_read: Fix regression caused by db15fcfa899e1fe4d6994f68ceb299921b8aa6f1 for empty...

acl_read: Fix regression caused by db15fcfa899e1fe4d6994f68ceb299921b8aa6f1 for empty lists

The original code never dereferenced attrs and only added "*" if attrs
was NULL (not if attrs[0] was NULL).

This causes significant performance issues with the new paged_results
module introduced for 4.10 as the initial GUID search requests no
attributes. This GUID search turns into a search for "*" and ends up
allocating memory for the entire database.

This never appears to cause changes in the final result set, only
intermediate processing.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=13836

Signed-off-by: Garming Sam <garming@catalyst.net.nz>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>
Autobuild-User(master): Andrew Bartlett <abartlet@samba.org>
Autobuild-Date(master): Fri Mar 29 18:37:29 UTC 2019 on sn-devel-144

(cherry picked from commit a2b1970a37836e46d6c9eb6bda9bd20185de96ce)