sync: removed ref to lsdb.

Sync now emits to a signal whenever a new LSA is detected, and the LSDB
listens to this signal.  Sync consults a function object gotten at ctor time
to determine LSA newness.  This means Sync no longer needs a reference to
the LSDB, and LSA newness criteria can be freely manipulated.

Change-Id: Ifce3ebfc921ad846fcfa12d99c78f3b337180827
refs: #4264
diff --git a/src/lsdb.hpp b/src/lsdb.hpp
index 8d01155..042d727 100644
--- a/src/lsdb.hpp
+++ b/src/lsdb.hpp
@@ -32,21 +32,9 @@
 #include <ndn-cxx/security/key-chain.hpp>
 #include <ndn-cxx/util/signal.hpp>
 #include <ndn-cxx/util/time.hpp>
-
 #include <utility>
 #include <boost/cstdint.hpp>
 
-#include <utility>
-#include <boost/cstdint.hpp>
-
-#include <ndn-cxx/security/key-chain.hpp>
-#include <ndn-cxx/util/time.hpp>
-
-#include <utility>
-#include <boost/cstdint.hpp>
-#include <ndn-cxx/security/key-chain.hpp>
-#include <ndn-cxx/util/time.hpp>
-
 namespace nlsr {
 
 class Nlsr;
@@ -411,6 +399,9 @@
   ndn::time::seconds m_adjLsaBuildInterval;
 
   SequencingManager m_sequencingManager;
+
+  ndn::util::signal::ScopedConnection m_onNewLsaConnection;
+
 };
 
 } // namespace nlsr