note i don't think this is a dup of bug 1240757 as you had original speculated, because you do not seem to have any bind9 or dnsmasq listening on 10.0.3.1.
Please attach your /etc/default/lxc-net file. Your lxc-net.log file showed an error opening /etc/lxc/dnsmasq.conf, but the line which would set that configuration file is commented out in the shipped /etc/default/lxc-net.
note i don't think this is a dup of bug 1240757 as you had original speculated, because you do not seem to have any bind9 or dnsmasq listening on 10.0.3.1.
Please attach your /etc/default/ lxc-net file. Your lxc-net.log file showed an error opening /etc/lxc/ dnsmasq. conf, but the line which would set that configuration file is commented out in the shipped /etc/default/ lxc-net.