dnsmasq: only listen on loopback :53, as local resolver

Even though dnsmasq only listened to requests from 127.0.0.1, port 53
was visible using nmap.  We only use dnsmasq as a local resolver, so
we can safely change the config to bind to loopback instead, and at
the same time get less noise from nmap scans.

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

board/common/rootfs/etc/dnsmasq.conf

@@ -2,8 +2,12 @@
 # managed by openresolv.  DHCP lease, VPN tunnel establishment,
 # and similar events feed servers and configuration to dnsmasq.
 domain-needed
-#interface=lo
-listen-address=127.0.0.1
+
+# Only listen to loopback (local system)
+interface=lo
+bind-dynamic
+#listen-address=127.0.0.1,::1
+
 enable-dbus
 
 # Generated by openresolv