jsnbd: removing dependency of the state_hook

[Jeremy Kerr]

Hi Igor,

> 
> Jeremy, I'm working on implementing a virtual media device interface
> type.
> Gerrit PRs: 
> https://gerrit.openbmc-project.xyz/q/topic:virtual_media_interface_type
> .
> 
> Actually `jsnbd:nbd-proxy` are depend on a call the `state_hook`
> which configures usb-gadget and inject the UDC. 
> By PR
> https://gerrit.openbmc-project.xyz/c/openbmc/meta-bytedance/+/35726
>  
> the related feature are moved to the `usb-ctrl` tool and 
> https://gerrit.openbmc-project.xyz/c/openbmc/meta-phosphor/+/33492
>  allows to use `usb-ctrl` in `state_hook` script.
> 
> May I kindly ask, can we avoid the call `state_hook` in `nbd-proxy`
> and move to directly call the `usb-ctrl` from it?

This would assume that all of the uses of the NBD channel are to be
exposed to the host over a USB endpoint.

As far as I know, we have at least one usage where this is not the
case.

The state hook is intended to be a per-platform customisation, so I
would be reluctant to remove it.

Regards,


Jeremy