Fixing failed grub boot for Cubbli 20 installs

There was a bug in Cubbli upgrader script, which prevented the boot loader from working on first boot. When this happens, press 'e' on the grub boot screen to get to boot loader configuration editor:

When you are in the editor you will see a screen like this (details might wary):

You need to edit three lines. The editor uses US keyboard layout, so '(' is shift+'9', ')' is shift+'0' and '/' is '-'. Replace the set root= line with:

set root=(hd0,gpt2)

And remove /boot from the start of linux and initrd lines. The end result should look like this:

After these edits you can boot successfully with CTRL + X. You will see one more message "error: no such device". Just hit enter to skip it. 

Sorry about this! Regads Jani Jaakkola, who sometimes forgets to test "trivial" changes.