Removed backward compatability with Geni AMv1 API.

The Geni AMv3 API return structure has a special exception in GetVersion, for backward compatibility with Geni AMv1: 
Next to "code", "output" and "value", the return struct for the getVersion call also contains "geni_api" (which is a duplicate of the "geni_api" in the "value").

This was copied in the federation AM API. However, I don't think this has any use, so I propose we remove it.