lifecycle hooks, nodeSelector for serviceDefaults

[Jancis]

This PR implements couple changes:

• nodeSelector for serviceDefaults;
• preStop delay by default, allows pod to be removed from service backends, but delays the application shutdown for 15 seconds for existing requests to finish. This may solve nginx connection errors.

If application allows graceful shutdown, it can react to SIGTERM calls and handle them. Node application can shut down express server like so:

const server = app.listen( ..

process.on('SIGTERM', () => {
  console.log('SIGTERM signal received: closing HTTP server in 10 seconds')

  const closeServer = () => server.close()
  setTimeout(closeServer, 10000)
})