fix: use more reliable close event

The close event from the request object is not guaranteed to fire on the
same order across major versions of Node.js, the more accurate way to
look if the connection was closed is to listen to the event on the
socket. Fixes tests on v16.

Ref: nodejs/node#38924

lib/plugins/bodyReader.js

@@ -186,7 +186,7 @@ function bodyReader(options) {
         // add 'close and 'aborted' event handlers so that requests (and their
         // corresponding memory) don't leak if client stops sending data half
         // way through a POST request
-        req.once('close', next);
+        req.socket.once('close', next);
         req.once('aborted', next);
         req.resume();
     }