In some situations, asynchronous EJB calls could result in the deployment's classloader being "leaked".
This occurred because the execute method could lead to new thread creation. When this occurs the new thread assigns itself the context classloader of the parent thread, which would be the classloader of the deployment. To prevent this the Thread Context Classloader (TCCL) is set to `null` before the execute method is invoked, and then restored afterwards.
Asynchronous EJB calls can no longer result in deployment classloader leaks.