Use get_notification_url when configuring notifications

If a project manually configures the oslo.messaging transport url for
notifications it should use 'get_notification_url', not
'get_transport_url'.  get_transport_url should only be used to obtain
the RPC transport address.

Change-Id: I77772dfa9f30a3db2db6d0387260dfe3452a26ef
Closes-Bug: #1708754
diff --git a/lib/nova b/lib/nova
index 8311a54..c988c2f 100644
--- a/lib/nova
+++ b/lib/nova
@@ -536,7 +536,7 @@
     # Set the oslo messaging driver to the typical default. This does not
     # enable notifications, but it will allow them to function when enabled.
     iniset $NOVA_CONF oslo_messaging_notifications driver "messagingv2"
-    iniset $NOVA_CONF oslo_messaging_notifications transport_url $(get_transport_url)
+    iniset $NOVA_CONF oslo_messaging_notifications transport_url $(get_notification_url)
     iniset_rpc_backend nova $NOVA_CONF
     iniset $NOVA_CONF glance api_servers "$GLANCE_URL"