Instead of reporting a hierarchy change, skip the folder and let the
client know that the folder no longer exists.
If we remove a folder on the server-side that cannot be removed on the
client-side we used to end up in an endless loop:
* Sync reports hierarchy change
* FolderSync fails
* Sync reports hierarchy change
* ...
Simply reporting that the folder has been removed seems like a less
aggressive approach that is in line with the protocol and works better
with Outlook (and should achieve the same as long as the client doesn't
ignore the STATUS_OBJECT_NOT_FOUND status code).