In addition to C locale there is also C.UTF-8 locale now. Filter that as
well, by using ${grub_lang}, which contains a stripped value.
This fixes the following message and resulting boot failure:
error: file `/boot/grub/locale/C.gmo' not found.
Signed-off-by: Christian Hesse <mail@eworm.de>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
