JarResourceManager leaks an InputStream when asked for a Resource for the root of a jar #17121
Description
Due to how Undertow's URLResource and the JDK's JarURLConnection work, if JarResourceManager is asked for an entry for the root of a jar (a path of "" or "/"), it will open an InputStream and never close it. To avoid this, we need to avoid asking the URLResource for its content length for such resources.