mgmt+face: allow MTU of datagram faces to be overridden

refs #4005

Change-Id: I01d98b88cdee41b633f6fb9a5600088efe8de749
diff --git a/daemon/face/ethernet-channel.cpp b/daemon/face/ethernet-channel.cpp
index 69c6f45..691b40b 100644
--- a/daemon/face/ethernet-channel.cpp
+++ b/daemon/face/ethernet-channel.cpp
@@ -203,7 +203,8 @@
 
   auto linkService = make_unique<GenericLinkService>(options);
   auto transport = make_unique<UnicastEthernetTransport>(*m_localEndpoint, remoteEndpoint,
-                                                         params.persistency, m_idleFaceTimeout);
+                                                         params.persistency, m_idleFaceTimeout,
+                                                         params.mtu);
   auto face = make_shared<Face>(std::move(linkService), std::move(transport));
 
   m_channelFaces[remoteEndpoint] = face;