Update release note for httpd keep alive

Adds information about change of default.

Change-Id: I9041345bbffefe6059d5ff151ebff07b6e26321a
Related: blueprint add-ssl-internal-network

releasenotes/notes/add-keep-alive-timeout-for-httpd-0d51a9d139c50f66.yaml

@@ -3,4 +3,9 @@ features:
   - |
     Adds configuration parameter ``kolla_httpd_keep_alive`` to configure the
     keep-alive timeout for services that use httpd to handle HTTP requests.
-    The default value is 60 seconds.
+    The default value is 60 seconds, overriding the httpd default of 5 seconds.
+upgrade:
+  - |
+    Adds configuration parameter ``kolla_httpd_keep_alive`` to configure the
+    keep-alive timeout for services that use httpd to handle HTTP requests.
+    The default value is 60 seconds, overriding the httpd default of 5 seconds.