Fix 'additive_only' parameter api-ref
Fix 'additive_only' parameter api-ref

The 'additive_only' patch was missing the "min_version" parameter
in the api-ref. This patch fixes that so users will know which API
version supports this parameter.

Change-Id: I05439ea1dd01c35bedcfc3eaa5d17ed8dd2ca348

openstack/octavia,openstack/octavia,openstack/octavia