I tried to reproduce this in raring and could not.
Is it possible for you to test in raring?
Please post your full /etc/network/interfaces.
Also, your demo.conf does not specify a custom rootfs, but your virt-install command uses /data/virt/lxc/demo01/rootfs. Is /var/lib/lxc a symlink on your system, or is something else going on?
I tried to reproduce this in raring and could not.
Is it possible for you to test in raring?
Please post your full /etc/network/ interfaces.
Also, your demo.conf does not specify a custom rootfs, but your virt-install command uses /data/virt/ lxc/demo01/ rootfs. Is /var/lib/lxc a symlink on your system, or is something else going on?