test: replace common.fixtureDir with fixtures

PR-URL: #15816
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

test/parallel/test-http2-compat-serverrequest-pipe.js

@@ -4,14 +4,15 @@
 const common = require('../common');
 if (!common.hasCrypto)
   common.skip('missing crypto');
+const fixtures = require('../common/fixtures');
 const assert = require('assert');
 const http2 = require('http2');
 const fs = require('fs');
 const path = require('path');
 
 // piping should work as expected with createWriteStream
 
-const loc = path.join(common.fixturesDir, 'person.jpg');
+const loc = fixtures.path('person.jpg');
 const fn = path.join(common.tmpDir, 'http2pipe.jpg');
 common.refreshTmpDir();