systemd: allow AF_NETLINK in ndn-autoconfig-client.service

It uses NetworkMonitor

Change-Id: I244f61578614307b13ed5b67981e1409e3d9e677
diff --git a/systemd/ndn-autoconfig-client.service.in b/systemd/ndn-autoconfig-client.service.in
index 668c4fb..1e76a74 100644
--- a/systemd/ndn-autoconfig-client.service.in
+++ b/systemd/ndn-autoconfig-client.service.in
@@ -50,7 +50,7 @@
 # effective setting of ProtectSystem=strict
 ProtectSystem=full
 ProtectSystem=strict
-RestrictAddressFamilies=AF_UNIX AF_INET AF_INET6
+RestrictAddressFamilies=AF_UNIX AF_NETLINK AF_INET AF_INET6
 RestrictNamespaces=yes
 RestrictRealtime=yes
 StateDirectory=ndn/ndn-autoconfig