firewalld: don't activate IPv6_rpfilter to be compatible with re6st

See https://firewalld.org/documentation/configuration/firewalld-conf.html#ipv6_rpfilter

When re6st is running with tunnels, the IPv6 packets can come in through
an interface and go out through another. This is expected.

component/firewalld/buildout.cfg

@@ -128,6 +128,7 @@ command =
 
   sed -i 's#DefaultZone=public#DefaultZone=trusted#' ${firewalld:etc-dir}/firewalld.conf
   sed -i 's#FirewallBackend=nftables#FirewallBackend=iptables#' ${firewalld:etc-dir}/firewalld.conf
+  sed -i 's#IPv6_rpfilter=yes#IPv6_rpfilter=no#' ${firewalld:etc-dir}/firewalld.conf
 
   sed -i "s#'/etc/firewalld'#'${firewalld:etc-dir}'#"     ${firewalld:python-egg}/firewall/config/__init__.py
   sed -i "s#'/usr/lib/firewalld'#'${firewalld:location}/lib/firewalld'#" ${firewalld:python-egg}/firewall/config/__init__.py