net: small code cleanup

`options` is already a param of the function.

PR-URL: https://github.com/nodejs/node/pull/3943
Reviewed-By: Evan Lucas <evanlucas@me.com>
Reviewed-By: Michaël Zasso <mic.besace@gmail.com>
Reviewed-By: Myles Borins <myles.borins@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

lib/net.js

@@ -1081,7 +1081,6 @@ function Server(options, connectionListener) {
   EventEmitter.call(this);
 
   var self = this;
-  var options;
 
   if (typeof options === 'function') {
     connectionListener = options;