I observed that libvirt-bin's networks failed to autostart despite being
so configure and when I attempted to manually (via virsh) start the network I got:

error: Failed to start network vmpriv
error: internal error: Failed to apply firewall rules /sbin/iptables --table filter --insert INPUT --in-interface virbr1 --protocol tcp --destination-port 67 --jump ACCEPT: Another app is currently holding the xtables lock. Perhaps you want to use the -w option?

After some time virsh is able to start the network but it appears that is another
process does firewall work (e.g. firewall is slow to start), then virsh fails to start
network due to the new xtables locking mechanism and failure of libvirt to use
the -w (wait) option.

Regards,

Daniel