grub-mkconfig prefers /etc/default/grub.d settings

[Andrey Bondarenko]

Since the fix for bug 901600 was commited, setting in /etc/default/grub now can be overiden by /etc/default/grub.d. It helps developers to make customized images, but it can really blows up the brain to the rest users.

I've lost an hour trying to understand why grub ignores my GRUB_TIMEOUT settings, until I found hostile file 50-cloudimg-settings.cfg, that silently overrides my setting. I think such behaviour violates simple principle — user settings must have the higest precedence.

I understand that changing this behaviour, may break a lot of code. So please at least add BIG RED BANNER to /etc/default/grub with warning: before changing something in the file, check all the files in /etc/default/grub.d for conflicting settings, because they have higher precedence.