Minor Description
The embedded jetty web server's WebAppClassloader holds up webapp's jar files and does not release them after close. For that reason the web app's temp dir cannot be cleaned up on Windows. (Other platforms like Linux doesn't prevent a force delete of files even they are not released).
As long as this behavior exists we need to have a workaround to let
the tmp dir be cleaned up.
It is possible that we use a 'customized' classloader to replace jetty's
WebAppClassloader, in which we manually iterate every JarFile resources
and close them.
