logic: disallow Interest loopback on sync prefix

In ChronoSync protocol, a party keeps an outstanding sync Interest
under a sync prefix that is registered by all parties including
itself. ndn-cxx's Interest loopback mechanism would cause a party
to receive its own sync Interest, which is undesirable.

refs #3979

Change-Id: I2709bc1005e966d9fb9b27c1dfde549fb6f01041

src/logic.cpp

@@ -111,7 +111,7 @@ Logic::Logic(ndn::Face& face,
 
   _LOG_DEBUG_ID("Listen to: " << m_syncPrefix);
   m_syncRegisteredPrefixId =
-    m_face.setInterestFilter(m_syncPrefix,
+    m_face.setInterestFilter(ndn::InterestFilter(m_syncPrefix).allowLoopback(false),
                              bind(&Logic::onSyncInterest, this, _1, _2),
                              bind(&Logic::onSyncRegisterFailed, this, _1, _2));