docker: Share sota dir with dockerd container

Share the sota dir with dockerd container so a user can bind mount local
directory or file located within the compose app dir which is
`/var/sota/compose-apps/<app>`. For example:

cat docker-compose.yml
```
...
volumes:
   - ./nginx.conf:/etc/nginx/nginx.conf:ro
...

```

Signed-off-by: Mike Sul <mike.sul@foundries.io>

docker/docker-compose.yml

@@ -7,6 +7,7 @@ services:
     volumes:
       - ${DOCKER_DATA_ROOT}:/var/lib/docker
       - docker-runtime:/var/run/docker
+      - ${SOTA_DIR}:/var/sota
     privileged: true
 
   sotactl: