Define 'links' as a common parameter type

Nova APIs contain a lot of 'links' parameter and the definitions of
each API are the same. This patch adds a common type for 'links' and
shares it between APIs for the maintenancebility.

Partially implements blueprint nova-api-attribute-test

Change-Id: I9609a9cadb0a7edd707fe57e76b3d629a0b3f8bc
Verify the list volume attributes of Nova APIs

This patch adds the JSON schema for volume list and
validate the response of Nova Volume list APIs with
added JSON schema to block the backward incompatibility
change in the future.

The response body of Nova APIs volume list-'os-volumes'
& volume list details-'os-volumes/detail' is the below:

{
    "volumes": [
        {
            "id": "a26887c6-c47b-4654-abb5-dfadf7d3f803",
            "status": "in-use",
            "displayName": "Volume Name",
            "availabilityZone": "zone1:host1",
            "createdAt": "1999-01-01T01:01:01",
            "displayDescription": "Volume Description"
            "volumeType": "Backup",
            "snapshotId": null,
            "metadata": {},
            "size": 100,
            "attachments": [
                {
                    "id": "a26887c6-c47b-4654-abb5-dfadf7d3f803",
                    "device": "/",
                    "volumeId": "a287c6-c47b-4654-abb5-dfadf7d3f803",
                    "serverId": "3912f4-c5ba-4aec-9165-872876fe202e"
                }
            ]
        }
    ]
}

Partially implements blueprint nova-api-attribute-test

Change-Id: I97bb6310a6fcb7d475dbd2bc53814d38c5e9c173
Merge "Verify the list volume attributes of Nova APIs"
Merge "Define 'links' as a common parameter type"