Fix for DNS fail in HTTP request

Closes GH-653.

lib/http.js

@@ -1166,6 +1166,13 @@ Agent.prototype._establishNewConnection = function() {
 
     req.emit('error', err);
     req._hadError = true; // hacky
+
+    // clean up so that agent can handle new requests
+    parser.finish();
+    socket.destroy();
+    self._removeSocket(socket);
+    parsers.free(parser);
+    self._cycle();
   });
 
   socket.ondata = function(d, start, end) {

test/simple/test-http-dns-fail.js

@@ -0,0 +1,40 @@
+/* 
+ * Repeated requests for a domain that fails to resolve
+ * should trigger the error event after each attempt.
+ */
+
+var common = require('../common');
+var assert = require('assert');
+var http = require('http');
+
+var resDespiteError = false
+var hadError = 0
+
+function httpreq(count) {
+  if ( 1 < count ) return
+
+  var req = http.request({
+    host:'not-a-real-domain-name.nobody-would-register-this-as-a-tld',
+    port: 80,
+    path: '/',
+    method: 'GET'
+  }, function(res) {
+    resDespiteError = true
+  });
+
+  req.on('error', function(e){
+    console.log(e.message);
+    hadError++
+    httpreq(count + 1)
+  })
+
+  req.end()
+}
+
+httpreq(0)
+
+
+process.on('exit', function() {
+  assert.equal(false, resDespiteError);
+  assert.equal(2, hadError);
+});