title: health check fails with 404 error after migrating to spring boot 2.x
body: <p>i'm new to spring boot and have just completed the migration of spring boot from 1.5 to 2.x for my app.
  Everything seems to be fine except for the /health check which fails on "localhost" consistently. I looked for references over the internet but couldn't find any. Have somebody come across this? What could be the issue ?</p>
  
  <pre><code>{
      "timestamp": "2018-08-29T07:06:02.3330000+00:00",
      "status": 404,
      "error": "Not Found",
      "message": "No message available",
      "path": "/health"
  }
  </code></pre>