replmd: Remove some redundant code

replmd: Remove some redundant code

At first glance, this code seemed completely unnecessary. However, it
was added (by commit f6bc4c08b19f5615) for a valid reason: adding the
whenChanged/uSNChanged attributes to the message can cause msg->elements
to be reallocated, which means the old_el pointer (which points to
msg->elements memory) can be out of date.

whenChanged/uSNChanged now get added to the msg last, just before the DB
modify operation. So old_el can no longer become out of date within
replmd_process_link_attribute(), so re-fetching it is now redundant.

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