update_container only works if base image hasn't changed

[Xarthisius]

If user changes base image (e.g. from JupyterLab to RStudio) and invokes update_container the task will fail, as it's not sufficient to simply update service with a new image. A rough list of things that should be done:

• verify if license volume should be mounted (modify service mounts)
• modify labels using new container_config
• modify command using new rendered_command
• modify env using new container_config
• modify resources using new container_config

It might be more practical to refactor _launch_container.