Stop services only on upgrade to Ocata or later

The undercloud upgrade process is now able to stop services itself,
so there is no need for the user to do so (and they should not, in
case part of the upgrade expects the services to be running).

This moves the service stop into a stable admonition and leaves an
explanation as to why it should not be done on Pike+.

bp undercloud-upgrade

Change-Id: Ifc52866d7f22427ec41e6ac616710e3e431dffe3

doc/source/install/installation/updating.rst

@@ -18,14 +18,21 @@ You can upgrade any packages that are installed on the undercloud machine.
 
     sudo yum clean all
 
-#. Stop services so that they are not restarted by packaging scripts
-   when they are updated. The service restarts will be handled by the
-   undercloud upgrade command after new configuration has been applied.::
-
-    sudo systemctl stop openstack-*
-    sudo systemctl stop neutron-*
-    sudo systemctl stop openvswitch
-    sudo systemctl stop httpd
+#. Stop all OpenStack-related services if upgrading to Ocata or an older release.
+   In Pike and later releases this step is handled by the undercloud upgrade
+   process and should not be done by the user.
+
+   .. admonition:: Stable Branch
+      :class: stable
+
+         Stop services so that they are not restarted by packaging scripts
+         when they are updated. The service restarts will be handled by the
+         undercloud upgrade command after new configuration has been applied.::
+
+            sudo systemctl stop openstack-*
+            sudo systemctl stop neutron-*
+            sudo systemctl stop openvswitch
+            sudo systemctl stop httpd
 
 #. Update the TripleO CLI package::