Investigate flaky test-fs-copyfile #15394

=== release test-fs-copyfile ===
Path: parallel/test-fs-copyfile
assert.js:43
  throw new errors.AssertionError({
  ^

AssertionError [ERR_ASSERTION]: 33188 === 33204
    at verify (/home/james/node/main/test/parallel/test-fs-copyfile.js:17:10)
    at Object.<anonymous> (/home/james/node/main/test/parallel/test-fs-copyfile.js:32:1)
    at Module._compile (module.js:600:30)
    at Object.Module._extensions..js (module.js:611:10)
    at Module.load (module.js:521:32)
    at tryModuleLoad (module.js:484:12)
    at Function.Module._load (module.js:476:3)
    at Function.Module.runMain (module.js:641:10)
    at startup (bootstrap_node.js:201:16)
    at bootstrap_node.js:626:3
Command: out/Release/node /home/james/node/main/test/parallel/test-fs-copyfile.js