nlsr: Don't use ndn aliases provided by ndn-cxx/common.hpp

refs: #3983

Change-Id: I31da8d68e0285dcfe9c7d3e5e678c00397d22bef
diff --git a/src/security/certificate-store.hpp b/src/security/certificate-store.hpp
index a90fc70..a45f0c4 100644
--- a/src/security/certificate-store.hpp
+++ b/src/security/certificate-store.hpp
@@ -35,7 +35,7 @@
 {
 public:
   void
-  insert(shared_ptr<ndn::IdentityCertificate> certificate)
+  insert(std::shared_ptr<ndn::IdentityCertificate> certificate)
   {
     if (certificate != nullptr) {
       // Key is cert name without version
@@ -43,7 +43,7 @@
     }
   }
 
-  shared_ptr<const ndn::IdentityCertificate>
+  std::shared_ptr<const ndn::IdentityCertificate>
   find(const ndn::Name& certificateNameWithoutVersion) const
   {
     CertMap::const_iterator it = m_certificates.find(certificateNameWithoutVersion);
@@ -63,7 +63,7 @@
   }
 
 private:
-  typedef std::map<ndn::Name, shared_ptr<ndn::IdentityCertificate>> CertMap;
+  typedef std::map<ndn::Name, std::shared_ptr<ndn::IdentityCertificate>> CertMap;
   CertMap m_certificates;
 };