title: log4j logger overwriting into jxl.log file
body: <p>I am using log4j for logger purpose. At the same time I am also using JXL to read/write Excel file.<br>
  But instead of writing log into log4j logger file, it is writing into <code>jxl.log</code> file.</p>
  
  <p>What can be issue?</p>