title: Failed to remove ThreadLocal when the web application was stopped with log4j2.0-rc1 configuration
body: <p>I implemented logging module using log4j2 for my web application. It's running on tomcat server. I was using log4j2-beta9 version earlier and deployed my application in test regions. Recently I migrated to log4j2.0-rc1 version of logging modules and enabled asynchronous logging.
  But when I shutdown my application, I am observing following errors in catalina.out. As per log4j2.0-rc1 release notes, similar issues were fixed under this latest release, but I am observing the similar errors</p>
  
  <p>SEVERE: The web application [/Example1] created a ThreadLocal with key of type [java.lang.ThreadLocal] (value [java.lang.ThreadLocal@1701b802]) and a value of type [org.apache.logging.log4j.core.async.AsyncLogger.Info] (value [org.apache.logging.log4j.core.async.AsyncLogger$Info@71d7971a]) but failed to remove it when the web application was stopped. Threads are going to be renewed over time to try and avoid a probable memory leak.</p>
  
  <pre><code>Exception in thread "Thread-3" java.lang.NoClassDefFoundError: org/apache/logging/log4j/core/config/NullConfiguration
          at org.apache.logging.log4j.core.LoggerContext.stop(LoggerContext.java:210)
          at org.apache.logging.log4j.core.async.AsyncLoggerContext.stop(AsyncLoggerContext.java:57)
          at org.apache.logging.log4j.core.LoggerContext$ShutdownThread.run(LoggerContext.java:437)
  Caused by: java.lang.ClassNotFoundException: org.apache.logging.log4j.core.config.NullConfiguration
          at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1714)
          at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1559)
  </code></pre>
  
  <p>I am not sure what could be the reason for this issue. Appreciate if anyone can explain the root cause for this issue. Is it issue with log4j2 library or with my application configuration.
  FYI, I am using RollingRandomAccessFile appender with system property 
  -DLog4jContextSelector=org.apache.logging.log4j.core.async.AsyncLoggerContextSelector.</p>