node: Need to explicitly specify MustBeFresh, othewise subsequent self-registrations will not work

refs #1141 (http://redmine.named-data.net/issues/1141)

Change-Id: Id852c29eb14037050735be71016789d774084875
diff --git a/src/node.cpp b/src/node.cpp
index 22f4963..fe192cc 100644
--- a/src/node.cpp
+++ b/src/node.cpp
@@ -147,6 +147,7 @@
       Interest interest(interestName);
       interest.setScope(1);
       interest.setInterestLifetime(1000);
+      interest.setMustBeFresh(true);
 
       expressInterest(interest, OnData(), OnTimeout());
         
@@ -188,6 +189,7 @@
   Interest interest(interestName);
   interest.setScope(1);
   interest.setInterestLifetime(1000);
+  interest.setMustBeFresh(true);
 
   expressInterest(interest,
                   func_lib::bind(&Node::registerPrefixFinal, this,