test: fix flaky cluster unix socket test

Ensure `common.tmpDir` exists before trying to chdir into it.  Fixes a
"ENOENT: no such file or directory, uv_chdir" error when the temporary
directory is removed before running the test.

PR-URL: #18263
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Jon Moss <me@jonathanmoss.me>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: Minwoo Jung <minwoo@nodesource.com>

test/parallel/test-cluster-net-listen-relative-path.js

@@ -20,6 +20,7 @@ assert.strictEqual(path.resolve(socketDir, socketName).length > 100, true,
 
 if (cluster.isMaster) {
   // ensure that the worker exits peacefully
+  common.refreshTmpDir();
   process.chdir(common.tmpDir);
   fs.mkdirSync(socketDir);
   cluster.fork().on('exit', common.mustCall(function(statusCode) {