Update nftables to allow libvirt traffic

system/base/nftables/templates/nftables.conf.j2

@@ -10,6 +10,9 @@ table inet filter {
                 # Accept any localhost traffic.
                 iif lo accept;
 
+                # Accept any libvirt traffic.
+                iifname virbr0 accept;
+
                 # Accept traffic originated from us.
                 ct state established,related accept;