Hey guys,
I had this same issue tonight when building an Ubuntu 16.04.01 Server VM. OS is installed fine and all seems well until I added my Unraid shares and rebooted. Suddenly, no network. Was seeing "Device not found" messages when trying to start the networking service. I did some digging and noticed that my nic used to be labeled enp2s2. After the shares were added and rebooted, I ran ip link only to find my nic is now labled enp2s6. After looking at the XML, I think it makes sense why. Below is a bit of the XML for this VM, AFTER I added the shares. Seems like the shares take precedence in the config file somehow and push the nic down to another slot. slot='0x06' in the config file apparently corresponds to enp2s6 nic label. To solve the problem, I was able to change the nic label in the /etc/network/interfaces config file and reboot. All is well again.
Hopefully, that makes sense and it helps someone else.
<filesystem type='mount' accessmode='passthrough'>
<source dir='/mnt/user/media/Movies/'/>
<target dir='Movies'/>
<alias name='fs0'/>
<address type='pci' domain='0x0000' bus='0x02' slot='0x01' function='0x0'/>
</filesystem>
<filesystem type='mount' accessmode='passthrough'>
<source dir='/mnt/user/media/TV/'/>
<target dir='TV'/>
<alias name='fs1'/>
<address type='pci' domain='0x0000' bus='0x02' slot='0x02' function='0x0'/>
</filesystem>
<filesystem type='mount' accessmode='passthrough'>
<source dir='/mnt/user/media/Kid Movies/'/>
<target dir='KidMovies'/>
<alias name='fs2'/>
<address type='pci' domain='0x0000' bus='0x02' slot='0x03' function='0x0'/>
</filesystem>
<filesystem type='mount' accessmode='passthrough'>
<source dir='/mnt/user/media/Kid TV/'/>
<target dir='KidTV'/>
<alias name='fs3'/>
<address type='pci' domain='0x0000' bus='0x02' slot='0x04' function='0x0'/>
</filesystem>
<filesystem type='mount' accessmode='passthrough'>
<source dir='/mnt/user/media/Music/'/>
<target dir='Music'/>
<alias name='fs4'/>
<address type='pci' domain='0x0000' bus='0x02' slot='0x05' function='0x0'/>
</filesystem>
<interface type='bridge'>
<mac address='52:54:00:c7:28:ff'/>
<source bridge='br0'/>
<target dev='vnet0'/>
<model type='virtio'/>
<alias name='net0'/>
<address type='pci' domain='0x0000' bus='0x02' slot='0x06' function='0x0'/>
</interface>