Comment 2 for bug 1998621

To reproduce the error I did the following:
 * connect onto my network-agent
 * enter the namespace of my network via ip netns exec qdhcp-$network_id bash
 * check with "ss -tuplen" that dnsmasq is listening on tcp/53
 * nc localhost 53 # keep this open
 * add/remove a subnet from the current network (or just call directory.get_plugin().agent_notifiers['DHCP agent'].network_added_to_agent() on your network_id/agent_host)
 * wait shortly
 * kill the netcat (it keeps the one dnsmasq process busy)
 * check "ss -tuplen" and see that it is no longer listening on tcp/53