XD-2097 Shutdown containers from admin

- Enable `shutdown` endpoint for containers
 - Keep the `mangementContextPath` the same for both admin/container
- ContainerRegistrar stores the container's port as container attribute
  - If the container uses local port `0` then the port is known only when
the `EmbeddedServletContainer` is initialized
    - Add `update` method in `ContainerRepository` to update the container data
    - Update container data (attributes) along with container port info
- Add REST endpoint that shuts down container by `containerId`
  - Get container host and port from container attributes
  - Use `RestTemplate` to send `POST` request to shutdown the container
  - Throw `NoSuchContainerException` if container is not found
  - Add test
Actually, I realized someone can change management port to be different than the server port. In any case, we should only use the management port to access the shutdown endpoint. I will update this to read "setManagementPort". Also, there will be couple of `EmbeddedServletContainerInitializedEvent` events (one for actual server and other for management server). Here we need the management server event. I will update the code accordingly.