I could be way way off - but why not simply increase the logging level for the right classes so the message you dont want to appear are ignored ?
Unfortunately there is no class associated with STDERR so as far as I can tell there is no way to configure log4j to not print out STDERR (or STDOUT) messages. Of course, someone could always prove me wrong. Or you could dig through the log4j source code and see if and how it could be done (that it the beauty of open source, after all), and then post thge solution here.
Actually, thinking about it again, try adding this to the log4j config file to turn it off (or add an appender-ref to rediect it to a specific appender):