net: remove unnecessary variables

PR-URL: #20864
Reviewed-By: Anatoli Papirovski <apapirovski@mac.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Tiancheng "Timothy" Gu <timothygu99@gmail.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: Daniel Bevenius <daniel.bevenius@gmail.com>

lib/net.js

@@ -1416,8 +1416,7 @@ Server.prototype.listen = function(...args) {
     throw new ERR_SERVER_ALREADY_LISTEN();
   }
 
-  var hasCallback = (cb !== null);
-  if (hasCallback) {
+  if (cb !== null) {
     this.once('listening', cb);
   }
   var backlogFromArgs =
@@ -1704,7 +1703,7 @@ if (process.platform === 'win32') {
     }
   };
 } else {
-  _setSimultaneousAccepts = function(handle) {};
+  _setSimultaneousAccepts = function() {};
 }
 
 module.exports = {