title: Authentication to Apache Drill is temporary failing
body: <p>I'm running a 5 Nodes Mapr Drill cluster, and everything is working fine, except that sometimes (can be multiple time during the day, sometimes once in a few days, no specific pattern), when I try to connect to one of the drillbits (Via Drill Web-UI / PyDrill), the login is failing with Invalid username/password error, even though the password and username are correct!
  Scripts that trying to open connections with PyDrill also failing with the same error.</p>
  <ol>
  <li>The issue is resolved by itself after a while, or when I restart the affected drillbit with maprcli command.</li>
  <li>this issue occurs only on specifc drillbits and not on all. (Usually node #1. It happens on others too, but only a few times. On the first node it happens almost on a daily basis)</li>
  <li>Login is failing with all users. Mapr user, AD users, etc.</li>
  </ol>
  <p>Did anyone encounter this? I'm trying to find the root cause and a solution. I suspect it is happening when the cluster is running on low memory so the login service (PAM) is failing.</p>
  <p>Thanks!</p>