face: close idle Datagram faces

refs #1281

Change-Id: Ifc766964f653d3991b55d76361c8b9bbe5d630cf
diff --git a/daemon/face/multicast-udp-face.cpp b/daemon/face/multicast-udp-face.cpp
index 49146ac..62b20eb 100644
--- a/daemon/face/multicast-udp-face.cpp
+++ b/daemon/face/multicast-udp-face.cpp
@@ -12,7 +12,7 @@
 
 
 MulticastUdpFace::MulticastUdpFace(const shared_ptr<MulticastUdpFace::protocol::socket>& socket)
-  : DatagramFace<protocol>(FaceUri(socket->local_endpoint()), socket)
+  : DatagramFace<protocol>(FaceUri(socket->local_endpoint()), socket, true)
 {
   NFD_LOG_DEBUG("Face creation. Multicast group: "
                 << m_socket->local_endpoint());