Fix compilation against the latest version of ndn-cxx

Remove Buffer.buf()

Change-Id: I9a460dd43e0b96220d3d44a63607408afa1b2473
diff --git a/src/client-module.cpp b/src/client-module.cpp
index b0f9825..67c6201 100644
--- a/src/client-module.cpp
+++ b/src/client-module.cpp
@@ -94,7 +94,7 @@
   certRequest.setName(Name(state->m_key.getName()).append("cert-request").appendVersion());
   certRequest.setContentType(tlv::ContentType_Key);
   certRequest.setFreshnessPeriod(time::hours(24));
-  certRequest.setContent(state->m_key.getPublicKey().buf(), state->m_key.getPublicKey().size());
+  certRequest.setContent(state->m_key.getPublicKey().get<uint8_t>(), state->m_key.getPublicKey().size());
   SignatureInfo signatureInfo;
   signatureInfo.setValidityPeriod(security::ValidityPeriod(time::system_clock::now(),
                                                            time::system_clock::now() + time::days(10)));
diff --git a/tests/identity-management-fixture.cpp b/tests/identity-management-fixture.cpp
index f2b7e1b..1eef608 100644
--- a/tests/identity-management-fixture.cpp
+++ b/tests/identity-management-fixture.cpp
@@ -99,7 +99,7 @@
   certificate.setFreshnessPeriod(time::hours(1));
 
   // set content
-  certificate.setContent(key.getPublicKey().buf(), key.getPublicKey().size());
+  certificate.setContent(key.getPublicKey().get<uint8_t>(), key.getPublicKey().size());
 
   // set signature-info
   SignatureInfo info;