Emit disconnected event instead of error when ECONNRESET

ECONNRESET means the other side of the TCP conversation abruptly
closed its end of the connection.

If we get an ECONNRESET error from the proxy request and the
socket is destroyed this means that the client has closed
his connection, and emit this as an error can lead to
confusion and hacks to filter that kind of message.

I think that the best we can do is abort and emit another event,
so if any caller wants to handle with that kind of error, he can
by listen the disconnected event.

http-party#813

Author: Deividy

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

@@ -132,7 +132,15 @@ web_o = Object.keys(web_o).map(function(pass) {
     req.on('error', proxyError);
 
     // Error Handler
-    proxyReq.on('error', proxyError);
+    proxyReq.on('error', function (err) {
+        if (req.socket.destroyed && err.code === 'ECONNRESET') {
+          server.emit('disconnected', err, req, res, options.target);
+          proxyReq.abort();
+        } else {
+          proxyError(err);
+        }
+    });
+
 
     function proxyError (err){
       if (clb) {

test/lib-http-proxy-passes-web-incoming-test.js

@@ -229,7 +229,7 @@ describe('#createProxyServer.web() using own http server', function () {
 
     var started = new Date().getTime();
     function requestHandler(req, res) {
-      proxy.once('error', function (err, errReq, errRes) {
+      proxy.once('disconnected', function (err, errReq, errRes) {
         proxyServer.close();
         expect(err).to.be.an(Error);
         expect(errReq).to.be.equal(req);