Comment # 5 on bug 994322 from Michael Chang

Well my idea is bascally similar to Steffen's, but the install scripts divided
by install_location.

Eg
 /usr/lib/bootloader/grub2/install_device_disk
 /usr/lib/bootloader/grub2/install_device_extended
 /usr/lib/bootloader/grub2/install_device_root
 /usr/lib/bootloader/grub2/install_device_boot

And we set install script to one of them

 ln -s /usr/lib/bootloader/grub2/install_device_mbr
/usr/lib/bootloader/grub2/install_00

In case we need secondary or third we increase that counter

 ln -s /usr/lib/bootloader/grub2/install_device_mbr
/usr/lib/bootloader/grub2/install_01

It's easy to get the install location by following the link, and if things go
wrong like the horrendous name scheme change it's easier to adapt the script
than config. :)