test: remove unnecessary assignments

common.js needs to be loaded in all tests so that there is checking
for variable leaks and possibly other things. However, it does not
need to be assigned to a variable if nothing in common.js is referred
to elsewhere in the test.

The main tradeoff for this bit of code churn is that it gets the code
base most of the way to being able to enable the no-unused-vars rule in
eslint.

(The non-tooling benefit is that it lessens cognitive load when reading
tests as it is an immediate indication that none of the functions or
properties in common.js will be used by the test.)

PR-URL: #4563
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>

Author: Trott

test/internet/test-dns-txt-sigsegv.js

@@ -1,5 +1,5 @@
 'use strict';
-var common = require('../common');
+require('../common');
 var assert = require('assert');
 var dns = require('dns');
 

test/internet/test-dns.js

@@ -1,5 +1,5 @@
 'use strict';
-var common = require('../common');
+require('../common');
 var assert = require('assert'),
     dns = require('dns'),
     net = require('net'),

test/internet/test-http-dns-fail.js

@@ -4,7 +4,7 @@
  * should trigger the error event after each attempt.
  */
 
-var common = require('../common');
+require('../common');
 var assert = require('assert');
 var http = require('http');
 

test/internet/test-net-connect-timeout.js

@@ -3,7 +3,7 @@
 // https://groups.google.com/forum/#!topic/nodejs/UE0ZbfLt6t8
 // https://groups.google.com/forum/#!topic/nodejs-dev/jR7-5UDqXkw
 
-var common = require('../common');
+require('../common');
 var net = require('net');
 var assert = require('assert');
 

test/internet/test-net-connect-unref.js

@@ -1,5 +1,5 @@
 'use strict';
-var common = require('../common');
+require('../common');
 var assert = require('assert');
 var net = require('net');
 

test/message/2100bytes.js

@@ -1,5 +1,5 @@
 'use strict';
-var common = require('../common');
+require('../common');
 var assert = require('assert');
 var util = require('util');
 

test/message/core_line_numbers.js

@@ -1,5 +1,5 @@
 'use strict';
-const common = require('../common');
+require('../common');
 const punycode = require('punycode');
 
 // This test verifies that line numbers in core modules are reported correctly.

test/message/error_exit.js

@@ -1,5 +1,5 @@
 'use strict';
-var common = require('../common');
+require('../common');
 var assert = require('assert');
 
 process.on('exit', function(code) {

test/message/eval_messages.js

@@ -1,6 +1,6 @@
 'use strict';
 
-var common = require('../common');
+require('../common');
 var assert = require('assert');
 
 var spawn = require('child_process').spawn;

test/message/hello_world.js

@@ -1,5 +1,5 @@
 'use strict';
-var common = require('../common');
+require('../common');
 var assert = require('assert');
 
 console.log('hello world');