dch-gw: Open Zabbix ports in the firewall

Obviously, the Zabbix agent (active and passive) ports need to be open
in order for the gateway device itself to be monitored by Zabbix.

group_vars/dch-gw/dch-network.yml

@@ -85,6 +85,8 @@ allow_incoming:
   port: bootps
 - protocol: tcp
   port: ssh
+- protocol: tcp
+  port: 10050
 
 
 allow_outgoing:
@@ -106,5 +108,7 @@ allow_outgoing:
   port: domain
 - protocol: udp
   port: ntp
+- protocol: tcp
+  port: 10051
 
 trace_dropped: true