Fix const correctness issues

cppcheck correctly notes that a lot of variables in the new code can be
const.  Make most of them const.

Tested: WIP

Signed-off-by: Ed Tanous <edtanous@google.com>
Change-Id: I8f37b6353fd707923f533e1d61c5b5419282bf23
diff --git a/redfish-core/lib/certificate_service.hpp b/redfish-core/lib/certificate_service.hpp
index 2fc606d..a4ecbf0 100644
--- a/redfish-core/lib/certificate_service.hpp
+++ b/redfish-core/lib/certificate_service.hpp
@@ -460,7 +460,7 @@
             sdbusplus::message::object_path csrObjectPath;
             m.read(csrObjectPath, interfacesProperties);
             BMCWEB_LOG_DEBUG << "CSR object added" << csrObjectPath.str;
-            for (auto& interface : interfacesProperties)
+            for (const auto& interface : interfacesProperties)
             {
                 if (interface.first == "xyz.openbmc_project.Certs.CSR")
                 {