replmd: Set GET_ANC if Windows sends a link with unknown source object

replmd: Set GET_ANC if Windows sends a link with unknown source object

Windows replication can send the linked attribute before it sends the
source object. The MS-DRSR spec says that in this case the client should
resend the GetNCChanges request with the GET_ANC flag set. In my testing
this resolves the problem - Windows will include the source object for the
linked attribute in the same replication chunk.

This problem doesn't happen with Samba-to-Samba replication, because the
source object for the linked attribute is guaranteed to have already been
sent.

Signed-off-by: Tim Beale <timbeale@catalyst.net.nz>
Reviewed-by: Garming Sam <garming@samba.org>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>
BUG: https://bugzilla.samba.org/show_bug.cgi?id=12972