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
Right, unless the port is set to use local port `0', this value will be the same as that of what we will see when processing `EmbeddedServletContainerInitializedEvent`. The reason this is added here because there is a valid option `-1` which user can set via XD_MGMT_PORT to disable management server. If that is set, then we will know when doing `updateManagementPort()`