public class LogLevelAdjuster
A JUnit method @Rule that changes the logger level for a set of classes
while a test method is running. Useful for performance or scalability tests
where we don't want to generate a large log in a tight inner loop.
As well as adjusting Log4j, this also adjusts loggers for logback. The amqp-client
library now uses slf4j. Since we have logback on the CP (for the appender)
we can't add the slf4j-log4j bridge as well.