title: mongo command writes to standard output AND pipe
body: <p>I can't write my head around the fact that the mongo command still display results on standard output, when the command is piped:</p>
  <pre><code>mongo --quiet  localhost:7017/admin -u $mongo_rootuser -p $mongo_rootpw --eval &quot;JSON.stringify(db.getUsers())&quot; | &lt;whatever command processes the output&gt;
  </code></pre>
  <p>I should not see anything printed on my console, since the result of the command is piped.</p>
  <p>Please, any workaround?
  (apart from asking mongo devs to respect basic posix)</p>