rib: simplify ReadvertisedRoute

refs #3818

Change-Id: Ied644d825458f387b6f886bfcd425cffd2c2c7aa
diff --git a/rib/readvertise/readvertise-destination.cpp b/rib/readvertise/readvertise-destination.cpp
index c064b23..3c577c7 100644
--- a/rib/readvertise/readvertise-destination.cpp
+++ b/rib/readvertise/readvertise-destination.cpp
@@ -24,14 +24,23 @@
  */
 
 #include "readvertise-destination.hpp"
+#include "core/logger.hpp"
 
 namespace nfd {
 namespace rib {
 
+NFD_LOG_INIT("ReadvertiseDestination");
+
 void
 ReadvertiseDestination::setAvailability(bool isAvailable)
 {
   if (m_isAvailable != isAvailable) {
+    if (isAvailable) {
+      NFD_LOG_DEBUG("Destination has become available.");
+    }
+    else {
+      NFD_LOG_DEBUG("Destinatino has become unavailable.");
+    }
     m_isAvailable = isAvailable;
     afterAvailabilityChange(isAvailable);
   }