dsdb: Make linked_attributes module GUID based for renames

dsdb: Make linked_attributes module GUID based for renames

This ensures that when we have the backlink out of sync with the forward link (perhaps due
to another operation that has put the backlink handling in an end-of-transaction
TODO list in repl_meta_data) that we do not error out, we just cope as well as we can.

The GUID is the unique identifier, not the DN.

Andrew Bartlett

Reviewed-by: Stefan Metzmacher <metze@samba.org>
Autobuild-User(master): Stefan Metzmacher <metze@samba.org>
Autobuild-Date(master): Sat Jan 12 12:52:28 CET 2013 on sn-devel-104