fs: check closing_ in FileHandle::Close

Fix possible flaky failure. Keep uv_fs_close from being called twice
on the same fd.

Signed-off-by: James M Snell <jasnell@gmail.com>

PR-URL: https://github.com/nodejs/node/pull/39472
Refs: https://github.com/nodejs/node/issues/39464


Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>