title: Elasticsearch cache clear doesn't seems to do what I expected
body: <p>I ran a search and the first time and it took 3-4 seconds.
  I ran the same search second time and it took less than 100 ms (as expected as it used the cache)
  Then I cleared the cache by calling "<a href="http://host:port/index/_cache/clear" rel="noreferrer">http://host:port/index/_cache/clear</a>"
  Next I ran the same search and was expecting it to take 3-4 seconds but it took less than 100 ms</p>
  
  <p>So the clearing of the cache didn't work?
  What exactly got cleared by that url?
  How I do make ES do the raw search (i.e. no caching) every time?</p>
  
  <p>I am doing as a part of some load testing.</p>