Add release note for services endpoint change

Add reno for:
- I1213a83ef8693c1cca1d20de974f7949a801d9f1
- Ib1103c00ddb7d6d624f4911147197d8355a3a6dd

Change-Id: Iecbbab5aeeade46b5cc238bc5542396e78db751c

releasenotes/notes/keystone_internal-53cc7b24ebdd9df4.yaml

@@ -0,0 +1,9 @@
+---
+other:
+  - |
+    Use Keystone internal endpoint instead of admin for services.
+    The admin endpoint is listening on the ctlplane network by default;
+    services should ideally be using the internal api network for this kind
+    of traffic, as the ctlplane network is mostly for provisioning. On the
+    other hand, the admin endpoint shouldn't be as relevant with services
+    switching to keystone v3.