encoding: remove duplicate buf() and get() methods from Buffer class

Change-Id: If885d4199d6c9df9b9b46664c3641c9a14a77eab
diff --git a/tests/identity-management-fixture.cpp b/tests/identity-management-fixture.cpp
index ecda82d..ee80dd1 100644
--- a/tests/identity-management-fixture.cpp
+++ b/tests/identity-management-fixture.cpp
@@ -115,7 +115,7 @@
   certificate.setFreshnessPeriod(time::hours(1));
 
   // set content
-  certificate.setContent(key.getPublicKey().buf(), key.getPublicKey().size());
+  certificate.setContent(key.getPublicKey().data(), key.getPublicKey().size());
 
   // set signature-info
   SignatureInfo info;