Websockets serving cached/wrong responses and potentially have incorrect headers in websocket

### Version

Vertx core 3.6.3 AND 3.7.0
NGINX 1.19.9

### Context

**Vertx 3.6.3**

We use NGINX 1.19.9 to proxy requests to our services in Kubernetes. One such service is a client manager that creates web sockets. For paths where the user in unauthorized, we call `client.reject(403)`.

Let's say client 1 connects to the service using `wss://myuri.com/api` and gets a valid 403. Great.
Now when client 2 connects to the service, the request handler appears to be re-using the request headers from client 1. The same is true for client 3, 4, 5, etc. Now all of our clients are in a bad state.

We've determined that it seems to be an interplay between nginx and vertx/netty. When we change upstream-keepalive-timeout to 0, the issue goes away. Only client 1 gets the 403. When we get rid of nginx entirely, the issue is also gone.

https://kubernetes.github.io/ingress-nginx/user-guide/nginx-configuration/configmap/#upstream-keepalive-timeout

### Do you have a reproducer?

**Vertx 3.7.0**

Reproducer code: https://github.com/NguyenVoDev/pure-vertx-js/blob/main/src/main/java/org/example/Server.java

Note this won't work if you try and repro locally, only if using nginx with keepalive set to > 0 (we have 60s). It could actually just be the headers nginx is adding to the request though

Instead of clients receiving headers from the existing web socket connection (like in 3.6.3), now the connections just hang and the websocket handler isn't even called.

### Extra

Are we supposed to be closing websockets after rejecting them?

* Java 11, Adopt openJDK