face: Transport::canChangePersistencyTo

Feasibility of transport persistency change can be checked with
Transport::canChangePersistencyTo before executing the actual change.
This enables management to verify persistency and other parameters
in a faces/update command before applying the updates.

Change-Id: Ia283f0daf678f47aad7b78b7e06dee4827f57cab
refs: #3232
diff --git a/daemon/face/websocket-transport.cpp b/daemon/face/websocket-transport.cpp
index 2fc331c..68fd08a 100644
--- a/daemon/face/websocket-transport.cpp
+++ b/daemon/face/websocket-transport.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /**
- * Copyright (c) 2014-2016,  Regents of the University of California,
+ * Copyright (c) 2014-2017,  Regents of the University of California,
  *                           Arizona Board of Regents,
  *                           Colorado State University,
  *                           University Pierre & Marie Curie, Sorbonne University,
@@ -77,15 +77,6 @@
 }
 
 void
-WebSocketTransport::beforeChangePersistency(ndn::nfd::FacePersistency newPersistency)
-{
-  if (newPersistency != ndn::nfd::FACE_PERSISTENCY_ON_DEMAND) {
-    BOOST_THROW_EXCEPTION(
-      std::invalid_argument("WebSocketTransport supports only FACE_PERSISTENCY_ON_DEMAND"));
-  }
-}
-
-void
 WebSocketTransport::doSend(Transport::Packet&& packet)
 {
   NFD_LOG_FACE_TRACE(__func__);