shutdown and memory leaks

[Zabrimus]

A valid shutdown of tomcat throws this message:
org.apache.catalina.loader.WebappClassLoaderBase.checkThreadLocalMapForLeaks
The web application [jonglisto-ng] created a ThreadLocal with key of type [java.lang.ThreadLocal] (value [java.lang.ThreadLocal@bd2d499]) and a value of type [io.netty.util.internal.InternalThreadLocalMap] (value [io.netty.util.internal.InternalThreadLocalMap@2b2309cb])
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.

It's necessary to try to find a solution to properly cleanup the netty InternalThreadLocalMap.