repl_meta_data: Fix removing of backlink on deleted objects

repl_meta_data: Fix removing of backlink on deleted objects

USER is memberOf GROUP and they both were deleted on W2K8R2 AD. Domain join ends
with error below.

Failed to apply records: ../source4/dsdb/samdb/ldb_modules/repl_meta_data.c:421
8: Failed to remove backlink of memberOf when deleting CN=USER\0ADEL:a1f2a2cc-1
179-4734-b753-c121ed02a34c,CN=Deleted Objects,DC=samdom,DC=intern: dsdb_module_
search_dn: did not find base dn CN=GROUP\0ADEL:030d0be1-3ada-4b93-8371-927f2092
3116,CN=Deleted Objects,DC=samdom,DC=intern (0 results): Operations error
Failed to commit objects: WERR_GEN_FAILURE/NT_STATUS_INVALID_NETWORK_RESPONSE

BUG: https://bugzilla.samba.org/show_bug.cgi?id=13120

Signed-off-by: Andrej Gessel <Andrej.Gessel@janztec.com>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>
Reviewed-by: Stefan Metzmacher <metze@samba.org>