message: Remove CoreOS, add Flatcar
diff: "sku": "7.5",
  "version": "latest"
  },
  - "CoreOS": {
  - "publisher": "CoreOS",
  - "offer": "CoreOS",
  - "sku": "Stable",
  - "version": "latest"
  - },
  "Debian": {
  "publisher": "Debian",
  "offer": "debian-10",
  "sku": "10",
  "version": "latest"
  },
  + "Flatcar": {
  + "publisher": "kinvolk",
  + "offer": "flatcar-container-linux-free",
  + "sku": "stable",
  + "version": "latest"
  + },
  "openSUSE-Leap": {
  "publisher": "SUSE",
  "offer": "openSUSE-Leap",
  