lorax-embed-repo: Stop using extlinux by default
lorax-embed-repo: Stop using extlinux by default

We're switching to GRUB2, which will support UEFI.

sujitfulse/rpm-ostree-toolbox,markllama/rpm-ostree-toolbox,tlitovsk/rpm-ostree-toolbox,projectatomic/rpm-ostree-toolbox,giuseppe/rpm-ostree-toolbox,maxamillion/rpm-ostree-toolbox,maxamillion/rpm-ostree-toolbox,giuseppe/rpm-ostree-toolbox,projectatomic/rpm-ostree-toolbox,maxamillion/rpm-ostree-toolbox,markllama/rpm-ostree-toolbox,sujitfulse/rpm-ostree-toolbox,tlitovsk/rpm-ostree-toolbox,projectatomic/rpm-ostree-toolbox,markllama/rpm-ostree-toolbox,maxamillion/rpm-ostree-toolbox,maxamillion/rpm-ostree-toolbox,sujitfulse/rpm-ostree-toolbox,projectatomic/rpm-ostree-toolbox,markllama/rpm-ostree-toolbox,markllama/rpm-ostree-toolbox,maxamillion/rpm-ostree-toolbox,tlitovsk/rpm-ostree-toolbox,giuseppe/rpm-ostree-toolbox,giuseppe/rpm-ostree-toolbox,tlitovsk/rpm-ostree-toolbox,sujitfulse/rpm-ostree-toolbox,sujitfulse/rpm-ostree-toolbox,markllama/rpm-ostree-toolbox,giuseppe/rpm-ostree-toolbox,tlitovsk/rpm-ostree-toolbox,sujitfulse/rpm-ostree-toolbox,tlitovsk/rpm-ostree-toolbox,projectatomic/rpm-ostree-toolbox,giuseppe/rpm-ostree-toolbox