new changes entry for rend_service_introduce refactoring

changes/bug6177

@@ -1,3 +1,5 @@
-  o Minor features:
+  o Code simplification and refactoring:
     - Add replaycache_t structure, functions and unit tests, for future use
       in refactoring rend_service_introduce() for bug 6177.
+    - Refactor rend_service_introduce() to be more clear to read, improve,
+      debug, and test. Bug 6177.