duplicate property in server show for volumes

Description
===========
Too many properties for volume attachments.
volumes, attached_volumes and volumes_attached have same info,
we can have volumes and attached_volumes (in pretty format).

Steps to reproduce
==================
- Add 2 volumes to server
- Run openstack server show cmd

 $ openstack server show demo_vm_2 --fit-width -c name, -c volumes_attached -c attached_volumes -c volumes

Actual result
=============

    +------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
    | Field | Value |
    +------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
    | attached_volumes | [{'device': None, 'id': '<_id>', 'volume_id': None, 'attachment_id': None, 'bdm_id': None, 'tag': None, 'delete_on_termination': False, 'name': None, 'location': None}, |
    | | {'device': None, 'id': '<_id1>', 'volume_id': None, 'attachment_id': None, 'bdm_id': None, 'tag': None, 'delete_on_termination': False, 'name': None, 'location': None}]|
    | volumes | [{'device': None, 'id': '<_id>', 'volume_id': None, 'attachment_id': None, 'bdm_id': None, 'tag': None, 'delete_on_termination': False, 'name': None, 'location': None}, |
    | | {'device': None, 'id': '<_id1>', 'volume_id': None, 'attachment_id': None, 'bdm_id': None, 'tag': None, 'delete_on_termination': False, 'name': None, 'location': None}]|
    | volumes_attached | attachment_id=, bdm_id=, delete_on_termination='False', device=, id='<_id>', location=, name=, tag=, volume_id= |
    | | attachment_id=, bdm_id=, delete_on_termination='False', device=, id='322549da-aeb1-496d-9cbc-9cb6214640c1', location=, name=, tag=, volume_id= |
    +------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------+

if above is not clear see here: https://paste.opendev.org/show/bVTSHATkNbIyS1mUDS9j/
Here we have 3 properties for volume attachments, and they all have almost the same data, "volumes" is enough; it gives the data that's really required.

Expected result
===============
Something like nova client:

    | os-extended-volumes:volumes_attached | [{"id": "<_id>", "delete_on_termination": false}, {"id": "<_id>", "delete_on_termination": false}] |

or only property for volumes.