Check list & search hypervisor attributes of Nova

This patch adds the JSON Schema for response of Nova V2 & V3
list & search hypervisor APIs and validate the response with added
JSON Schema to block the backward incompatibility change in the future.

The response body of V2 & V3 list & search hypervisor API is same
& given below:

{
    "hypervisors": [
        {
            "id": 1,
            "hypervisor_hostname": "fake-mini",
        }
    ]
}

Partially implements blueprint nova-api-attribute-test

Change-Id: I3929794061e0709561f905cd053249d36afb0a82
Merge "Check list & search hypervisor attributes of Nova"