security+examples+tests: Updating examples and tests for the updated security API

Change-Id: Ie3f37bf3d0002a35333812b0dec582e7d3567d42
diff --git a/examples/producer.cpp b/examples/producer.cpp
index bfff287..d7d1048 100644
--- a/examples/producer.cpp
+++ b/examples/producer.cpp
@@ -84,7 +84,7 @@
                                DEFAULT_PUBLIC_KEY_DER, sizeof(DEFAULT_PUBLIC_KEY_DER),
                                DEFAULT_PRIVATE_KEY_DER, sizeof(DEFAULT_PRIVATE_KEY_DER));
 
-    keyChain_.identities().addCertificateAsDefault(*keyChain_.identities().selfSign(keyName));
+    keyChain_.addCertificateAsDefault(*keyChain_.selfSign(keyName));
   }
   ////////////////////////////////////////////////////////////////////////////////////////
   ////////////////////////////////////////////////////////////////////////////////////////