Ensure we set compute upgrade_level

With this change, we are enabling OpenStack compute services
to automatically determine the highest available RPC level
to use based on the service versions in the deployment.

Change-Id: I4e08de92ab8d0641398f3b54d7ea87d83c3b050a
Closes-Bug: #1825999

templates/rocky/nova.conf

@@ -127,6 +127,9 @@ volume_api_class=nova.volume.cinder.API
 {% endfor -%}
 {% endif %}
 
+[upgrade_levels]
+compute = auto
+
 {% include "section-zeromq" %}
 
 {% include "parts/database-v2" %}