Don’t forget, until dracut 060 comes out there is a new service file which must be included in the initramfs. See here: https://bbs.archlinux.org/viewtopic.php?id=290450
So the full resume conf should look like this:
add_dracutmodules+=" resume "
install_items+=" /usr/lib/systemd/system/systemd-hibernate-resume.service "
After you add the service file you will need to rebuild the initramfs.
sudo dracut-rebuild