Network connection leak

When using Asynchronous servlets and AsyncListeners for long polling we observe a connection leak in the undertow subsystem.

Heap dumps show a large number of org.xnio.io.NioSocketConduit, io.undertow.server.protocol.http.HttpServerConnection and related objects.

However, since the effective number of connections is far less, nearly all AsyncContext instances we find are in a complete state and lsof output returns a large number of sockets with 'can't identify protocol' entries indicating that sockets are kept open by the JVM but are in fact half closed by the network stack.

Not all connections appear to be leaking, but over time, depending on the load, the server instance fills up.