code review fix

Change-Id: Ie616543094aaa31d596980ba7a3cef05de4351fc
diff --git a/src/challenge/challenge-credential.cpp b/src/challenge/challenge-credential.cpp
index cac5aa0..51ba94c 100644
--- a/src/challenge/challenge-credential.cpp
+++ b/src/challenge/challenge-credential.cpp
@@ -135,7 +135,7 @@
 
 Block
 ChallengeCredential::genChallengeRequestTLV(Status status, const std::string& challengeStatus,
-                                            std::multimap<std::string, std::string>&& params)
+                                            const std::multimap<std::string, std::string>& params)
 {
   Block request(tlv::EncryptedPayload);
   if (status == Status::BEFORE_CHALLENGE) {