Core/DBLayer: Refine new query callback for chaining

(cherry picked from commit 73e61fa652d1233bfff1db91fa2bca8c317c8caf)

src/server/database/Database/QueryCallbackProcessor.h

@@ -33,6 +33,9 @@ public:
     void ProcessReadyQueries();
 
 private:
+    QueryCallbackProcessor(QueryCallbackProcessor const&) = delete;
+    QueryCallbackProcessor& operator=(QueryCallbackProcessor const&) = delete;
+
     std::vector<QueryCallbackNew> _callbacks;
 };