Remote API methods that generate URLs (e.g. export space) are not cluster compatible

As an example, see the exportSpace remote API. This will return a URL from where the client can then download the result.

However, in a cluster it is possible that the HTTP request for the result will be sent to a different server from that which fulfilled the remote API request.

In this case the resource won't be found on this other node, and whats more the DownloadGateKeeper may not allow access.