[Merge] ~philroche/livecd-rootfs/+git/livecd-rootfs:bugfix/xenial-update-grub-manual-grub-pc-bin into livecd-rootfs:ubuntu/xenial

[Philip Roche]

https://bugs.launchpad.net/ubuntu/+source/livecd-rootfs/+bug/2045418 is the bug that this MP addresses 
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https://code.launchpad.net/~philroche/livecd-rootfs/+git/livecd-rootfs/+merge/456775
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