LoggerConfig#waitForCompletion is not thread safe

This is in trunk, svn commit 1608156

LoggerConfig#waitForCompletion uses an AtomicInteger counter to try to detect if there are any calls currently executing the log(Event) method, but it does not do so in a thread safe manner. Consider two threads A and B, where Thread A is calling clearAppenders(), and Thread B is calling log(Event),

Thread A  loggerConfig.clearAppenders()
Thread A  loggerConfig.waitForCompletion()
Thread A  counter.get() //returns 0
Thread A  //loggerConfig.waitForCompletion() returns

Thread B  loggerConfig.log(Event)
Thread B  counter.increment()

Thread A  proceeds assuming no log calls are onging, but thread B is in the log method

I'm not sure what the requirements are, but if the requirement is to not lose logging events, I think you need some sort of synchronization outside of the LoggerConfig object.