Bump to 20cdfff
    
    * f897ff0 README: add notes for CLI invocation
    * 3870e93 coreos-installer: clear the trap handler after umount
    * 4bc7da9 coreos-installer: move reboot logic to dracut service
    * efe979d coreos-installer: make sure we run as root
    * 666303d coreos-installer: verify boot partition device
    * 520ff67 coreos-installer: make new mount_boot_partition function
    * 4bc70c3 dracut: alphabetical sort of dracut dependencies
    * c4703a0 coreos-installer: add check for image download exit status
    * 33ba62e Use `dd conv=sparse`
    * e5d01c7 30coreos-installer: drop unused inst_modules
    * 7cba048 *: drop dialog