**breaking change**: Switch Face and related classes to v2::KeyChain

security::v2::KeyChain is now exposed as ndn::KeyChain, which should
ensure that dependent code can be mostly compiled.  However, expect code
that explicitly uses the old KeyChain interface to be broken.

Change-Id: I7330d0250d92f3f0f2570ab6d0214ab3dfdd18cc
Refs: #3098
diff --git a/src/security/command-interest-signer.hpp b/src/security/command-interest-signer.hpp
index 6c5e2ce..730260d 100644
--- a/src/security/command-interest-signer.hpp
+++ b/src/security/command-interest-signer.hpp
@@ -67,7 +67,7 @@
 {
 public:
   explicit
-  CommandInterestSigner(v2::KeyChain& keyChain);
+  CommandInterestSigner(KeyChain& keyChain);
 
   /**
    * @brief Create CommandInterest
@@ -82,10 +82,10 @@
    * @sa https://redmine.named-data.net/projects/ndn-cxx/wiki/CommandInterest
    */
   Interest
-  makeCommandInterest(const Name& name, const SigningInfo& params = v2::KeyChain::getDefaultSigningInfo());
+  makeCommandInterest(const Name& name, const SigningInfo& params = KeyChain::getDefaultSigningInfo());
 
 private:
-  v2::KeyChain& m_keyChain;
+  KeyChain& m_keyChain;
 };
 
 } // namespace security