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/power.hpp b/redfish-core/lib/power.hpp
index 031657a..ffe0ed5 100644
--- a/redfish-core/lib/power.hpp
+++ b/redfish-core/lib/power.hpp
@@ -139,7 +139,7 @@
             };
         getValidChassisPath(asyncResp, std::move(getChassisPath));
     }
-    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)