Retested with 2.02-2ubuntu8.6:
dannf@mdraid:~$ sudo grub-reboot 0
WARNING: Detected GRUB environment block on diskfilter device 0 will remain the default boot entry until manually cleared with: grub-editenv /boot/grub/grubenv unset next_entry
Retested with 2.02-2ubuntu8.6:
dannf@mdraid:~$ sudo grub-reboot 0
WARNING: Detected GRUB environment block on diskfilter device
0 will remain the default boot entry until manually cleared with:
grub-editenv /boot/grub/grubenv unset next_entry