we probably could use net ads search "(sAMAccountName=<machine_name>\$)" to find out OU. and then pass it to net ads join as "createcomputer" param.

https://bugzilla.samba.org/show_bug.cgi?id=12696

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/overlays/chromiumos-overlay/+/83a9e77c1914b7170b286e941d230bd3683f162b

commit 83a9e77c1914b7170b286e941d230bd3683f162b
Author: Zentaro Kavanagh <zentaro@google.com>
Date: Sat Mar 25 02:38:14 2017

Add patches for 2 bugs [1, 2] we found in Samba.

The first causes a failure obtaining group policy if any of the GPO
objects don't have a set of expected attributes.

The second is to properly support pre-created computer accounts. Without
the path Samba will create a new account in the default location rather
than using an existing account in a non-default OU.

[1] - https://bugzilla.samba.org/show_bug.cgi?id=12695
[2] - https://bugzilla.samba.org/show_bug.cgi?id=12696

BUG= chromium:703351 ,chromium:685663, chromium:701533 
TEST=emerges and patches tested at runtime

Change-Id: Id7680219f89240b349f512b0f1913a24bd99211e
Reviewed-on: https://chromium-review.googlesource.com/457284
Commit-Ready: Zentaro Kavanagh <zentaro@google.com>
Tested-by: Zentaro Kavanagh <zentaro@google.com>
Reviewed-by: Thiemo Nagel <tnagel@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>

[add] https://crrev.com/83a9e77c1914b7170b286e941d230bd3683f162b/net-fs/samba/files/samba-4.5.3-reuse_existing_computer_account.patch
[add] https://crrev.com/83a9e77c1914b7170b286e941d230bd3683f162b/net-fs/samba/files/samba-4.5.3-skip_missing_ldap_attributes.patch
[modify] https://crrev.com/83a9e77c1914b7170b286e941d230bd3683f162b/net-fs/samba/samba-4.5.3.ebuild
[rename] https://crrev.com/83a9e77c1914b7170b286e941d230bd3683f162b/net-fs/samba/samba-4.5.3-r6.ebuild

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/overlays/chromiumos-overlay/+/0b87f9bae1641df7ffc17dc746bab12e8a057e1b

commit 0b87f9bae1641df7ffc17dc746bab12e8a057e1b
Author: Lutz Justen <ljusten@chromium.org>
Date: Thu Mar 30 16:04:01 2017

authpolicy: Depend on latest Samba

Picks up CL:457284, which fixes two bugs.

BUG= chromium:701533 , chromium:685663
TEST=Compiles.

Change-Id: I026ec01c0a52f8ed12d401a2370cadc8bc226f7c
Reviewed-on: https://chromium-review.googlesource.com/463306
Commit-Ready: Roman Sorokin <rsorokin@chromium.org>
Tested-by: Roman Sorokin <rsorokin@chromium.org>
Reviewed-by: Roman Sorokin <rsorokin@chromium.org>

[modify] https://crrev.com/0b87f9bae1641df7ffc17dc746bab12e8a057e1b/chromeos-base/authpolicy/authpolicy-9999.ebuild

bulk Verify of older or not-user-facing Chromad bugs