Ubuntu 17.10 won't install GRUB - vdisk on /dev/hdc

I'm trying to install Ubuntu into a fresh VM container on unRAID v6.3.5. Everything goes ok until it gets to the point where it wants to install GRUB and spits out the error "unable to install GRUB on /dev/vda".

Doing research on this issue I learn that not only is it a long standing issue (Since at least Ubuntu 12) but the error comes from when the virtual disk is not the first device. Looking at the XML I see the ISO is at /dev/hda and the virtual disk is at /dev/hdc:

Quote

 <disk type='file' device='disk'>
      <driver name='qemu' type='raw' cache='writeback'/>
      <source file='/mnt/user/domains/Minecraft/vdisk1.img'/>
      <target dev='hdc' bus='virtio'/>
      <boot order='1'/>
      <address type='pci' domain='0x0000' bus='0x02' slot='0x03' function='0x0'/>
    </disk>
    <disk type='file' device='cdrom'>
      <driver name='qemu' type='raw'/>
      <source file='/mnt/user/isos/ubuntu-17.10-server-amd64.iso'/>
      <target dev='hda' bus='sata'/>
      <readonly/>
      <boot order='2'/>
      <address type='drive' controller='0' bus='0' target='0' unit='0'/>
    </disk>

Simply swapping the dev value doesn't resolve the issue, and it was suggested on the unRAID Reddit forum that the address line also need to be modified. Which I unfortunately do not have any idea what to change.

So my question is two fold: What should I modify in the above XML so the ISO and the virtual disks are properly swapped so (hopefully) Ubuntu will install grub, and how do I modify the underlying unRAID template for Ubuntu so future VMs don't need any changes?