Handle multiple initrd paths, as used in some distros

• Handle multiple initrd paths, as used in some distros

  From: "General Chaos"

  Manjaro uses two paths on the initrd line, e.g.:

    initrd /boot/intel-ucode.img /boot/initramfs-4.4-x86_64.img

  In addition to this change, handling this correctly when updating the grub menu requires fixing https://bugs.debian.org/838177 in grub (see grub-team/grub!26 (closed)), so that it can consume the output of this os-prober version successfully.

  [Commit message added by Simon McVittie smcv@collabora.com]

  Closes: #820838

• Re-indent previous commit

  No functional changes.