test: avoid running fsync on directory on AIX

On AIX the underlying fsync system call returns EBADF on a file
descriptor for an open directory. So avoid running fsync on it.

PR-URL: #21298
Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

test/parallel/test-fs-utimes.js

@@ -35,7 +35,11 @@ function stat_resource(resource) {
   if (typeof resource === 'string') {
     return fs.statSync(resource);
   } else {
+    const stats = fs.fstatSync(resource);
     // ensure mtime has been written to disk
+    // except for directories on AIX where it cannot be synced
+    if (common.isAIX && stats.isDirectory())
+      return stats;
     fs.fsyncSync(resource);
     return fs.fstatSync(resource);
   }