Use raw headers instead parsed.

Set-Cookie headers are parsed into single header with cookies in array.
This messes up the Set-Cookie headers, because browser receives multiple Set-Cookie headers as single with cookies separted with comma.

lib/http-proxy/passes/ws-incoming.js

@@ -114,8 +114,10 @@ var passes = exports;
       if (proxyHead && proxyHead.length) proxySocket.unshift(proxyHead);
 
       socket.write('HTTP/1.1 101 Switching Protocols\r\n');
-      socket.write(Object.keys(proxyRes.headers).map(function(i) {
-        return i + ": " + proxyRes.headers[i];
+      socket.write(proxyRes.rawHeaders.map(function(v, i, a) {
+        return !(i % 2) ? v + ": " + a[i+1] : null;
+      }).filter(function (v) {
+        return v ? true : false;
       }).join('\r\n') + '\r\n\r\n');
       proxySocket.pipe(socket).pipe(proxySocket);