I reported on IRC to Serge that virbr0 did indeed have STP enabled, but that I did not see any obvious dnsmasq errors. He already had diagnosed the problem & said as a workaround I could just change the 'start on' in /etc/init/console.conf in my container to 'start on mounted MOUNTPOINT=/run'. stgraber's new upstart will fix it properly when it hits the archive.
I reported on IRC to Serge that virbr0 did indeed have STP enabled, but that I did not see any obvious dnsmasq errors. He already had diagnosed the problem & said as a workaround I could just change the 'start on' in /etc/init/ console. conf in my container to 'start on mounted MOUNTPOINT=/run'. stgraber's new upstart will fix it properly when it hits the archive.