Enable unused variable warnings and resolve

This commit enables the "unused variables" warning in clang.  Throughout
this, it did point out several issues that would've been functional
bugs, so I think it was worthwhile.  It also cleaned up several unused
variable from old constructs that no longer exist.

Tested:
Built with clang.  Code no longer emits warnings.

Downloaded bmcweb to system and pulled up the webui, observed webui
loads and logs in properly.

Change-Id: I51505f4222cc147d6f2b87b14d7e2ac4a74cafa8
Signed-off-by: Ed Tanous <ed@tanous.net>
diff --git a/redfish-core/lib/message_registries.hpp b/redfish-core/lib/message_registries.hpp
index 63aa5f3..77fc10e 100644
--- a/redfish-core/lib/message_registries.hpp
+++ b/redfish-core/lib/message_registries.hpp
@@ -44,8 +44,8 @@
     /**
      * Functions triggers appropriate requests on DBus
      */
-    void doGet(crow::Response& res, const crow::Request& req,
-               const std::vector<std::string>& params) override
+    void doGet(crow::Response& res, const crow::Request&,
+               const std::vector<std::string>&) override
     {
         // Collections don't include the static data added by SubRoute because
         // it has a duplicate entry for members
@@ -83,7 +83,7 @@
     }
 
   private:
-    void doGet(crow::Response& res, const crow::Request& req,
+    void doGet(crow::Response& res, const crow::Request&,
                const std::vector<std::string>& params) override
     {
         if (params.size() != 1)
@@ -169,7 +169,7 @@
     }
 
   private:
-    void doGet(crow::Response& res, const crow::Request& req,
+    void doGet(crow::Response& res, const crow::Request&,
                const std::vector<std::string>& params) override
     {
         if (params.size() != 2)