test: fix flaky test-benchmark-fs

test-benchmark-fs uses common.tmpDir without first insuring it exists by
calling common.refreshTmpDir(). Add that function call.

PR-URL: https://github.com/nodejs/node/pull/17853
Reviewed-By: Jon Moss <me@jonathanmoss.me>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>

test/parallel/test-benchmark-fs.js

@@ -3,6 +3,8 @@
 const common = require('../common');
 const runBenchmark = require('../common/benchmark');
 
+common.refreshTmpDir();
+
 runBenchmark('fs', [
   'n=1',
   'size=1',