net_uv: fix test/simple/test-pipe-file-to-http.js

lib/net_uv.js

@@ -378,6 +378,8 @@ function afterWrite(status, handle, req, buffer) {
   assert.equal(req, req_);
 
   if (self._writeRequests.length == 0) {
+    // TODO remove all uses of ondrain - this is not a good hack.
+    if (self.ondrain) self.ondrain();
     self.emit('drain');
   }