Fixing problem by the fact that the localLevelReset() method in the Logger class

inadvertently uses the DEBUG_INT value in the org.slf4j.spi.LocationAwareLogger 
interface instead of the DEBUG_INT value in ch.qos.logback.classic.Level class. 

The issue was first identified by Andy Ruch in a message to the logback-user list
  http://qos.ch/pipermail/logback-user/2009-February/000955.html