refactor code to use defaults

Author: kai-ion

src/aws-cpp-sdk-core/source/config/EndpointResolver.cpp

@@ -17,10 +17,9 @@ namespace Aws
         {
             Aws::String ToEnvSuffix(const Aws::String& serviceId)
             {
-                Aws::String result = serviceId;
-                std::transform(result.begin(), result.end(), result.begin(), ::toupper);
-                std::replace(result.begin(), result.end(), ' ', '_');
-                std::replace(result.begin(), result.end(), '-', '_');
+                Aws::String result = Utils::StringUtils::ToUpper(serviceId.c_str());
+                Utils::StringUtils::Replace(result, " ", "_");
+                Utils::StringUtils::Replace(result, "-", "_");
                 return result;
             }