fixes #893 Query string invalid

https://play.lighthouseapp.com/projects/82401-play-20/tickets/893


I have a question about that line in framework/src/play/src/main/scala/play/core/server/netty/PlayDefaultUpstreamHandler.scala

```scala
val rCookies = getCookies(nettyHttpRequest)
```
rCookies is never used, why?