Add a version API test for Nova v3 API

The version API of Nova returns the API version information with the
following body:
  {"version":
    {"id": "v3.0",
     "status": "EXPERIMENTAL",
     "updated": "2013-07-23T11:33:21Z",
     ..
    }
  }

This patch adds the API test.

Partially implements blueprint nova-v3-api-tests

Change-Id: Ibd6c3b4f3228340b265cbc9a0e7fe2dbc93c691c
Merge "Add a version API test for Nova v3 API"