fib: don't refresh neighbor router's FIB entry (it is already installed w/ expiry=never)

refs: #4799

Change-Id: Ib55687655ccd8673eeae14d8418e458ad8ab00aa
diff --git a/src/route/fib-entry.cpp b/src/route/fib-entry.cpp
index a3186b3..0091245 100644
--- a/src/route/fib-entry.cpp
+++ b/src/route/fib-entry.cpp
@@ -26,7 +26,7 @@
 INIT_LOGGER(route.FibEntry);
 
 void
-FibEntry::writeLog()
+FibEntry::writeLog() const
 {
   NLSR_LOG_DEBUG("Name Prefix: " << m_name);
   NLSR_LOG_DEBUG("Seq No: " << m_seqNo);