back to use protected keychain

Change-Id: I6f69fbea2640c78ac73a2d372978729154779383
diff --git a/tests/identity-management-fixture.hpp b/tests/identity-management-fixture.hpp
index 9bae058..9b10dbf 100644
--- a/tests/identity-management-fixture.hpp
+++ b/tests/identity-management-fixture.hpp
@@ -90,7 +90,7 @@
   security::Certificate
   addCertificate(const security::Key& key, const std::string& issuer);
 
-public:
+protected:
   KeyChain m_keyChain;
 };