getncchanges.py: Add test for replicating reanimated objects

getncchanges.py: Add test for replicating reanimated objects

Reading between the lines, this scenario seems to be the main reason
that Microsoft added the GET_TGT flag. MS AD can handle getting links
for unknown targets OK, but if it receives links for a deleted/recycled
target then it would tend to drop the received links. Samba client also
used to drop the links if talking to a Microsoft DC (or a Samba server
with GET_TGT support).

The specific scenario is the client side already knows about a deleted
object. That object is then re-animated and used as the target for a
linked attribute. *Then* the target object gets updated again so it gets
sent in a later replication chunk to the linked attribute, i.e. the
client receives the link before it learns that the target object has
been re-animated.

In this test we're interested in particular at how the client behaves
when it receives a linked attribute for a deleted object. (It *should*
retry with GET_TGT to make sure the target is up-to-date. However, it
was just dropping the linked attribute).

To exercise the client-side, we disable replication, setup the
links/objects on one DC the way we want them, then force a replication
to the second DC. We then check that when we query each DC, they both
tell us about the links/objects we're expecting (i.e. no links got
lost).

Note that this wasn't a problem with older versions of Samba-to-Samba
because sending the links last guaranteed that the target objects were
always up-to-date.

Signed-off-by: Tim Beale <timbeale@catalyst.net.nz>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>
Reviewed-by: Garming Sam <garming@catalyst.net.nz>