While integrating the changes to grub2 config stage options in the
`osbuild/images` repository, I noticed that the code for grub2.legacy
is embedding the grub2 stage config options struct in its own config
options struct [1]. However, the grub2 stage options contain also the
`default` entry, while the grub2.legacy stage does not allow this option
in its stage options.
This change fixes that and ensures that the grub2 stage options config
section is a subset of the grub2.legacy stage options config section.
[1] d5644f3115/pkg/osbuild/grub2_legacy_stage.go (L85)
Signed-off-by: Tomáš Hozza <thozza@redhat.com>