Add  create and delete to Jumpgate volume API

    1. Support SL portable storage create operation via jumpdate
    2. Support SL portable storage delete operation via jumpdate
    3. Add unittest coverage for jumpgate volume create/delete

Change-Id: I9cd6acb0832279fdfa5080e728ecaef9ac9de638
This is the request body from cinderclient when running cinder create 1

REQ: curl -i http://localhost:5000/volume/v1/333582/volumes -X POST -H "User-Agent: python-cinderclient" -H "Content-Type: application/json" -H "Accept: application/json" -H "X-Auth-Token: SG1NekZBRGthYTFnNG9XK0oreEZwN2JTa05RdS9YSDJmaG9xYjkraWNkY3lncFFWRi82RDFhMjhTaVZHb1dQWFpvc21EczZZRUtvUnFTNk5JTElQSUV2RHF5ZWVnRFBzZWg2cjk1OERNV3Axb080U0IvYSsyeURVT0tNSTYrOENDNTkwWmVhczVoVXUwM3ZCUWVUK3BvMFdqVW1Gc0E0aVJsZHZKT2VRNUtLUDBtalF0dFpDNE5Cb1ovaUhuUnd4SDM3RFVraXNkQk54aThpOGJQbmMwalJqTzJTNTlTaUdTSWJDbHo0SjBxQVp5VHFjcGdaL2FiSzlTSUF6RHorMWNIMHJmNmMwRlN6OVJTVXBsWXY0N3RUanhmZE9TaWMrZGVPenFlU3QrbFE9" -d '{"volume": {"status": "creating", "availability_zone": null, "source_volid": null, "display_description": null, "snapshot_id": null, "user_id": null, "size": 1, "display_name": null, "imageRef": null, "attach_status": "detached", "volume_type": null, "project_id": null, "metadata": {}}}'

The "display_name" is null which is still valid for Jason and it turns into None after json.loads().