Added MESOS-9518 to 1.5.3 CHANGELOG.

(cherry picked from commit ea824dca48d1dc839b41fd9fdfff71f2673c40aa)
diff --git a/CHANGELOG b/CHANGELOG
index 51609b5..08bbb74 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -9,6 +9,7 @@
   * [MESOS-9411] - Validation of JWT tokens using HS256 hashing algorithm is not thread safe.
   * [MESOS-9419] - Executor to framework message crashes master if framework has not re-registered.
   * [MESOS-9492] - Persist CNI working directory across reboot.
+  * [MESOS-9518] - CNI_NETNS should not be set for orphan containers that do not have network namespace.
 
 
 Release Notes - Mesos - Version 1.5.2