Remove extra copy operations identified by Coverity

Change-Id: I5e900082d3b17300f3a4ef95561d04c0228aba4f

libwvdrmengine/cdm/core/test/url_request.cpp

@@ -120,7 +120,7 @@ bool UrlRequest::GetResponse(std::string* message) {
     }
   }
 
-  ConcatenateChunkedResponse(response, message);
+  ConcatenateChunkedResponse(std::move(response), message);
   LOGV("HTTP response from %s: (%zu): %s", socket_.url().c_str(),
        message->size(), message->c_str());
   return true;