title: Can't turn off HtmlUnit logging messages
body: <p>I'm using HtmlUnit to interact with a web page that interacts with the server via Ajax.  Soon after the Ajax code starts, HtmlUnit produces these two log messages:</p>
  
  <pre>WARNING: Ignoring XMLHttpRequest.setRequestHeader for Content-length: it is a restricted header
  Mar 3, 2011 3:32:47 PM com.gargoylesoftware.htmlunit.javascript.host.xml.XMLHttpRequest jsxFunction_setRequestHeader
  WARNING: Ignoring XMLHttpRequest.setRequestHeader for Connection: it is a restricted header
  Mar 3, 2011 3:32:47 PM com.gargoylesoftware.htmlunit.javascript.host.xml.XMLHttpRequest jsxGet_status</pre>
  
  <p>...Followed by this message, repeated six times:</p>
  
  <pre>SEVERE: XMLHttpRequest.status was retrieved before the response was available.
  Mar 3, 2011 3:32:47 PM com.gargoylesoftware.htmlunit.javascript.host.xml.XMLHttpRequest jsxGet_status</pre>
  
  <p>I can't figure out how to turn these messages off.  Trawling through the code shows that they're produced by direct calls to a logger, not via a handler object that I could provide a do-nothing implementation for, as I already do for CSS errors.  The <a href="http://htmlunit.sourceforge.net/logging.html">HtmlUnit logging page</a> indicates that adding this code should work:</p>
  
  <pre><code>System.getProperties().put("org.apache.commons.logging.simplelog.defaultlog", "fatal");
  </code></pre>
  
  <p>...but it has no effect.  I also tried adding the following option where I invoke java:</p>
  
  <pre><code>-Dorg.apache.commons.logging.simplelog.defaultlog=fatal
  </code></pre>
  
  <p>...but that also has no effect.</p>
  
  <p>I guess I could redirect stderr to /dev/null while this code is executing, but are any less hacky solutions available?</p>