"openstack volume create" sending null values in create requests

[Lars Kellogg-Stedman]

The "openstack volume create" command is sending null values for unset fields in create requests. For example, when running "openstack volume create --size 1 testvolume", the result request is:

  {
  "volume": {
    "status": "creating",
    "user_id": null,
    "name": "testvolume",
    "imageRef": null,
    "availability_zone": null,
    "description": null,
    "multiattach": false,
    "attach_status": "detached",
    "volume_type": null,
    "metadata": {},
    "consistencygroup_id": null,
    "source_volid": null,
    "snapshot_id": null,
    "project_id": null,
    "source_replica": null,
    "size": 1
  }
  }

Unset fields should probably be omitted from the request rather than sent as null.