controller: use a single keychain

Fixes crash due to inconsistent keychains between contact-manager,
controller and the face.

Change-Id: I8adcd0767e36d7447468899eabd0debcf4185380
diff --git a/src/controller-backend.hpp b/src/controller-backend.hpp
index 2e3aa9f..adf60a8 100644
--- a/src/controller-backend.hpp
+++ b/src/controller-backend.hpp
@@ -149,17 +149,17 @@
 private:
   bool m_isNfdConnected;
   bool m_shouldResume;
-  ndn::Face m_face;
 
   Name m_identity;  //TODO: set/get
 
   Name m_localPrefix;
 
+  ndn::KeyChain m_keyChain;
+  ndn::Face m_face;
+
   // Contact Manager
   ContactManager m_contactManager;
 
-  // Security related;
-  ndn::KeyChain m_keyChain;
   shared_ptr<ndn::security::Validator> m_validator;
   ndn::security::ValidatorNull m_nullValidator;