adding device with containers/{id}/update api call has no effect

[yuvalbenshalom]

I am trying to add a volume to a running container with "containers update" API call(http) but I can't find the new volume in the container.
I am adding device to the devices array in the JSON as described in:
https://docs.docker.com/engine/api/v1.32/#operation/ContainerUpdate

example for a call I use:

curl --unix-socket /var/run/docker.sock -H "Content-Type: application/json" \
  http://v1.32/containers/5fe0f2708b65/update \
-d '{"Devices": [{"CgroupPermissions": "rwm","PathInContainer": "/tmp/varmount","PathOnHost": "/tmp/dst"}]}' -v

the call is successful response:

*   Trying /var/run/docker.sock...
* Connected to v1.32 (/Users/yuvalbs/Library/Containers/com.docker.) port 80 (#0)
> POST /containers/5fe0f2708b65/update HTTP/1.1
> Host: v1.32
> User-Agent: curl/7.54.0
> Accept: */*
> Content-Type: application/json
> Content-Length: 103
> 
* upload completely sent off: 103 out of 103 bytes
< HTTP/1.1 200 OK
< Api-Version: 1.32
< Content-Length: 18
< Content-Type: application/json
< Date: Mon, 04 Dec 2017 09:52:19 GMT
< Docker-Experimental: false
< Ostype: linux
< Server: Docker/17.09.0-ce (linux)
< 
{"Warnings":null}
* Connection #0 to host v1.32 left intact

API version: 1.32
server version: Docker/17.09.0-ce
host os: osx