While the default iptables setup used by Fedora/RHEL distros
only restricts traffic on the INPUT and/or FORWARD rules,
some users might have custom firewalls that restrict the
OUTPUT rules too.

These can prevent DHCP/DNS/TFTP responses from dnsmasq
from reaching the guest VMs. We should thus whitelist
these protocols in the OUTPUT chain, as well as the
INPUT chain.
Signed-off-by: NMalina Salina <malina.salina@protonmail.com>

Initial patch then modified to add unit tests and IPv6
support
Reviewed-by: NMichal Privoznik <mprivozn@redhat.com>
Signed-off-by: NDaniel P. Berrangé <berrange@redhat.com>