test: remove unused variables form http tests

The http tests seem especially prone to including unused variables.
This change removes them.

PR-URL: https://github.com/nodejs/node/pull/4422
Reviewed-By: Johan Bergström <bugs@bergstroem.nu>

test/parallel/test-http-localaddress-bind-error.js

@@ -17,7 +17,7 @@ var server = http.createServer(function(req, res) {
 });
 
 server.listen(common.PORT, '127.0.0.1', function() {
-  var req = http.request({
+  http.request({
     host: 'localhost',
     port: common.PORT,
     path: '/',