test: add support for NODE_TEST_DIR on a separate mount point

Linux permits a filesystem to be mounted at multiple points, but
`fs.renameSync` does not work across different mount points, even if the
same filesystem is mounted on both.
This fixes failing tests when NODE_TEST_DIR mount point is different
from the one on which the tests are executed (E.G. on a separate
partition).

Ref: http://man7.org/linux/man-pages/man2/rename.2.html

PR-URL: #21552
Refs: http://man7.org/linux/man-pages/man2/rename.2.html
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Ben Coe <bencoe@gmail.com>

test/parallel/test-fs-copyfile.js

@@ -64,7 +64,7 @@ try {
 } catch (err) {
   assert.strictEqual(err.syscall, 'copyfile');
   assert(err.code === 'ENOTSUP' || err.code === 'ENOTTY' ||
-    err.code === 'ENOSYS');
+    err.code === 'ENOSYS' || err.code === 'EXDEV');
   assert.strictEqual(err.path, src);
   assert.strictEqual(err.dest, dest);
 }

test/parallel/test-fs-error-messages.js

@@ -303,6 +303,11 @@ function re(literals, ...values) {
         `ENOTEMPTY: directory not empty, rename '${existingDir}' -> ` +
         `'${existingDir2}'`);
       assert.strictEqual(err.errno, uv.UV_ENOTEMPTY);
+    } else if (err.code === 'EXDEV') {  // not on the same mounted filesystem
+      assert.strictEqual(
+        err.message,
+        `EXDEV: cross-device link not permitted, rename '${existingDir}' -> ` +
+            `'${existingDir2}'`);
     } else if (err.code === 'EEXIST') {  // smartos and aix
       assert.strictEqual(
         err.message,