Provide original WebSocket exception instead of cause, close AsyncHttpClient#1392

Motivation:

The WebSocketHandler notifies the WebSocket with the cause Exception.
This way loses information, and cause might be null.

Mofivivation:

Propagate original exception

Result:

User has more information about the crash

Author: slandelle

client/src/main/java/org/asynchttpclient/netty/handler/WebSocketHandler.java

@@ -148,7 +148,7 @@ public void handleException(NettyResponseFuture<?> future, Throwable e) {
         try {
             NettyWebSocket webSocket = getNettyWebSocket(future);
             if (webSocket != null) {
-                webSocket.onError(e.getCause());
+                webSocket.onError(e);
                 webSocket.sendCloseFrame();
             }
         } catch (Throwable t) {