Update postinst file to follow v2 security elements

Change-Id: I17e11e05043ba864052419604096e72a6238ec9c
diff --git a/ndn-tools/debian/ndnping.postinst b/ndn-tools/debian/ndnping.postinst
index 09502a5..8b04456 100644
--- a/ndn-tools/debian/ndnping.postinst
+++ b/ndn-tools/debian/ndnping.postinst
@@ -6,7 +6,7 @@
 
 APP=ndnping
 
-if [ ! -f /var/lib/ndn/$APP/.ndn/ndnsec-public-info.db ]; then
+if [ ! -f /var/lib/ndn/$APP/.ndn/pib.db ]; then
     # Create HOME and generate self-signed NDN certificate
     sudo mkdir -p /var/lib/ndn/$APP/.ndn
     sudo chown -R ndn:ndn /var/lib/ndn/$APP