Support volume workload

[rawdaGastan]

Description

A new Volume workload has been added to ZOS and grid-client. It should act the same as ZMounts with some extra enhancements in performance as it go through less layers of virtualization.

Note: raw images are not supported

Interface

The new workload is of type volume and has the same structure as ZMount:

{
    "size": <size-in-bytes>
}