smoke test: test firewall inbound / outbound (#240)

Test that basic inbound / outbound firewall rules work during the smoke
test. This change sets an inbound firewall rule on host3, and a new
host4 with outbound firewall rules. It also tests that conntrack allows
packets once the connection has been established.

.github/workflows/smoke/genconfig.sh

@@ -2,6 +2,7 @@
 
 set -e
 
+FIREWALL_ALL='[{"port": "any", "proto": "any", "host": "any"}]'
 
 if [ "$STATIC_HOSTS" ] || [ "$LIGHTHOUSES" ]
 then
@@ -48,13 +49,6 @@ tun:
   dev: ${TUN_DEV:-nebula1}
 
 firewall:
-  outbound:
-    - port: any
-      proto: any
-      host: any
-
-  inbound:
-    - port: any
-      proto: any
-      host: any
+  outbound: ${OUTBOUND:-$FIREWALL_ALL}
+  inbound: ${INBOUND:-$FIREWALL_ALL}
 EOF