Fix cppcheck warnings

Signed-off-by: George Liu <liuxiwei@inspur.com>
Change-Id: If5d808b9cb3bc733e7e21d546247d745ac5e1bf8
diff --git a/src/watch.hpp b/src/watch.hpp
index a44480c..c206316 100644
--- a/src/watch.hpp
+++ b/src/watch.hpp
@@ -39,7 +39,8 @@
     virtual void callback(Context ctx) = 0;
 
     /** @brief Invoke the callback associated with the watch. */
-    virtual void callback(Context ctx, sdbusplus::message::message& msg){};
+    virtual void callback(Context /* ctx */,
+                          sdbusplus::message::message& /* msg */){};
 };
 
 } // namespace monitoring