lib: use req.socket over deprecated req.connection (#6705)

Signed-off-by: Sebastian Beltran <bjohansebas@gmail.com>

test/req.protocol.js

@@ -39,7 +39,7 @@ describe('req', function(){
         app.enable('trust proxy');
 
         app.use(function(req, res){
-          req.connection.encrypted = true;
+          req.socket.encrypted = true;
           res.end(req.protocol);
         });