Use standard BLOB,KEY,NACK as contentType instead of customized types

Change-Id: I792e19b8f1e2aa359605da44074fc25bf7963a9a
diff --git a/src/daemon/rrset-factory.cpp b/src/daemon/rrset-factory.cpp
index a75c650..9395f42 100644
--- a/src/daemon/rrset-factory.cpp
+++ b/src/daemon/rrset-factory.cpp
@@ -216,7 +216,7 @@
   Data data(name);
   data.setContent(cert.wireEncode());
 
-  setContentType(data, NDNS_BLOB, ttl);
+  setContentType(data, NDNS_KEY, ttl);
   sign(data);
   rrset.setData(data.wireEncode());