Add quota_set detail test for Nova v3 API

"get quota_set detail" API has been added since Nova v3 API, and the
returns the following body as a response:

  {"quota_set": {
     "id": "e9f3b1c3952e49369d9a02b6bc495cae",
     "instances": {"reserved": 0, "limit": 10, "in_use": 1},
     "cores": {"reserved": 0, "limit": 20, "in_use": 1},
     "ram": {"reserved": 0, "limit": 51200, "in_use": 64},
     ...
  }}

This patch adds a test for this API.

Partially implements blueprint nova-v3-api-tests

Change-Id: I5eb6f5e14065aeb7f56fb5a6a1095786773d167a
Merge "Add quota_set detail test for Nova v3 API"