Ubuntutemplate

I am not sure how you feel about trailing whitespace; my editor automatically trimmed that. I am also something of a git newbie so this PR includes 2 commits that could easily be 1. I'm certainly willing to redo this if there is a better way.

Basically, I've found that if you use the defaults in the ubuntu template to install ubuntu as non-LVM, grub-bhyve can find the default grub config. But if you install ubuntu with LVM, you need to set img_grub_d to "-d /grub" to find the installed ubuntu's grub config. I prefer this to setting img_grub_cfg since kernel upgrades would require changing img_grub_cfg as ubuntu kernel and initrd files include their kernel version.