Return complete response from services_client

Currently compute services_client returns Response by
removing top key from Response.
For example-
 return service_client.ResponseBody(resp, body['service'])

As service clients are in direction to move to Tempest-lib, all
service clients should return Response without any truncation.
One good example is Resource pagination links which are lost with current
way of return value. Resource pagination links are present in parallel
(not inside) to top key of Response.

This patch makes compute services_client to return
complete Response body.

Change-Id: I79bc3c14700c3201e8c8ac50e80d5f49c96e52c2
Implements: blueprint method-return-value-and-move-service-clients-to-lib
4 files changed