face: Implementing new "isOnDemand" flag

This flags replaces isPermanent flag in datagram faces, but with the
reversed logic (isPermanent = !isOnDemand)

Change-Id: I37ba604e5f105ca95a79a08b8cfc3d640df8b412
Refs: #1376
diff --git a/daemon/face/multicast-udp-face.cpp b/daemon/face/multicast-udp-face.cpp
index 62b20eb..f0e752b 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, true)
+  : DatagramFace<protocol>(FaceUri(socket->local_endpoint()), socket, false)
 {
   NFD_LOG_DEBUG("Face creation. Multicast group: "
                 << m_socket->local_endpoint());