Verify "enable a service" API response attributes

Now most attributes of Nova v2/v3 APIs are not checked in Tempest,
and this patch adds some tests which check these attributes to block
the backward incompatibility change in the future.

This patch adds the checks of "enable a service" API responses.

The response body of the API is the below:

  {
    "service": {
      "status": "enabled",
      "binary": "nova-compute",
      "host": "localhost-dev"
    }
  }

Partially implements blueprint nova-api-attribute-test

Change-Id: I17fca6383ad7079e9cea2adc1065f9e718def3cd
Merge "Verify "enable a service" API response attributes"
Merge branch 'master' of https://github.com/openstack/tempest