Incorrect Error mappings in 8040 code

The new 8040 code returns bogus errors when trying to create data resources which already exist via post.

Instead of returning 409 (same as the old code) or another appropriate 4xx code for a conflict it returns 503 - server failed. This is broken, there is no server failure, the server did its job and determined that a conflict is in place. It should neither pollute the logs nor return bogus error codes to the client.