Improve loops & fix cpp check warning

- This commit improves certain while loops to range based for loops.

- This commit also fixes the cppcheck warning that mentions about
  performance issues when using postfix operators on non-primitive
  types.

Tested By:
- A function is unittested.
- GET on both EthernetInterfaces & certificate service
  looks good without any issues.

Signed-off-by: Manojkiran Eda <manojkiran.eda@gmail.com>
Change-Id: I85420f7bf9af45a97e1a93b916f292c2516f5802
diff --git a/redfish-core/lib/managers.hpp b/redfish-core/lib/managers.hpp
index 26c2125..c621de3 100644
--- a/redfish-core/lib/managers.hpp
+++ b/redfish-core/lib/managers.hpp
@@ -1520,7 +1520,7 @@
             std::string& type = containerPair.first;
 
             for (nlohmann::json::iterator it = container->begin();
-                 it != container->end(); it++)
+                 it != container->end(); ++it)
             {
                 const auto& name = it.key();
                 BMCWEB_LOG_DEBUG << "looking for " << name;