Hunormous file rename for v3 to v2.1 for Compute

Nova team decided to do a minor version to 2.1
rather than move to v3 so the API docs need to
reflect that. Still marked Experimental.

Closes-bug:1367307

Change-Id: I59adfcae589b9481efcf0bdb8c4d63e54ceb6a1b
Merge "Hunormous file rename for v3 to v2.1 for Compute"