Hard-coded timeout for asynchronous HTTP requests - add async context timeout undertow option

public class AsyncContextImpl implements AsyncContext { 

private final List<BoundAsyncListener> asyncListeners = new CopyOnWriteArrayList<>(); private final HttpServerExchange exchange; private final ServletRequest servletRequest; private final ServletResponse servletResponse; 
private final TimeoutTask timeoutTask = new TimeoutTask(); 
private final ServletRequestContext servletRequestContext; 
private final boolean requestSupplied; private AsyncContextImpl previousAsyncContext;//the previous async context 

//todo: make default configurable 

private volatile long timeout = 30000; 
private volatile XnioExecutor.Key timeoutKey;