test: refactor test-http-unix-socket

Use `common.mustCall()` and `common.fail()` where appropriate.

Change `assert.equal` to `assert.strictEqual` to ensure specificity.

Change var declarations to const to take advantage of ES6 immutable
bindings.

PR-URL: #10072
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Santiago Gimeno <santiago.gimeno@gmail.com>

test/parallel/test-http-unix-socket.js

@@ -1,9 +1,9 @@
 'use strict';
-var common = require('../common');
-var assert = require('assert');
-var http = require('http');
+const common = require('../common');
+const assert = require('assert');
+const http = require('http');
 
-var server = http.createServer(function(req, res) {
+const server = http.createServer(function(req, res) {
   res.writeHead(200, {
     'Content-Type': 'text/plain',
     'Connection': 'close'
@@ -23,8 +23,8 @@ server.listen(common.PIPE, common.mustCall(function() {
   };
 
   var req = http.get(options, common.mustCall(function(res) {
-    assert.equal(res.statusCode, 200);
-    assert.equal(res.headers['content-type'], 'text/plain');
+    assert.strictEqual(res.statusCode, 200);
+    assert.strictEqual(res.headers['content-type'], 'text/plain');
 
     res.body = '';
     res.setEncoding('utf8');
@@ -34,19 +34,18 @@ server.listen(common.PIPE, common.mustCall(function() {
     });
 
     res.on('end', common.mustCall(function() {
-      assert.equal(res.body, 'hello world\n');
-      server.close(function(error) {
-        assert.equal(error, undefined);
-        server.close(function(error) {
-          assert.equal(error && error.message, 'Not running');
-        });
-      });
+      assert.strictEqual(res.body, 'hello world\n');
+      server.close(common.mustCall(function(error) {
+        assert.strictEqual(error, undefined);
+        server.close(common.mustCall(function(error) {
+          assert.strictEqual(error && error.message, 'Not running');
+        }));
+      }));
     }));
   }));
 
   req.on('error', function(e) {
-    console.log(e.stack);
-    process.exit(1);
+    common.fail(e.stack);
   });
 
   req.end();