v1.18.0

Note: CoreOS images have got removed on AWS, GCP, and DigitalOcean. If you're still running CoreOS on those providers, you'll need to build your own CoreOS image.

• Add support for setting arbitrary feature gates on the kubelet (#821)
• Fix the Docker installation on RHEL8 (#826)
• Fix hanging reboot on auto-update on Flatcar Linux (#824)