close websocket if proxyReq is closed before upgrade

avoids leaving client sockets open when upstream
connections are rejected.

Author: minrk

Diff for: lib/http-proxy/passes/ws-incoming.js

@@ -89,6 +89,11 @@ var passes = exports;
     );
     // Error Handler
     proxyReq.on('error', onOutgoingError);
+    proxyReq.on('response', function (res) {
+      // if upgrade event isn't going to happen, close the socket
+      // so we don't leave it hanging.
+      if (!res.upgrade) socket.end();
+    });
 
     proxyReq.on('upgrade', function(proxyRes, proxySocket, proxyHead) {
       proxySocket.on('error', onOutgoingError);