Description of problem:
In the Horizon "network topology" page, when an instance is created elsewhere (e.g. "nova boot"), the instance automatically appears in the topology diagram without any user intervention. However when an instance is removed (e.g. "nova delete") then the instance is not removed from the topology diagram until the page is manually refreshed. A removed instance should disappear from the topology diagram without user intervention.
Version-Release number of selected component (if applicable):
RHOSP8. The browser used to access Horizon is Chrome (version 56.0.2924.76).
Steps to Reproduce:
1. Spawn an instance using "nova boot" command.
2. Check the status in already opened browser. New instance is showing without need of refreshing the window.
3. Delete the instance. Browser is not reflecting the status until we are refreshing the browser.
Browser refresh needed to reflect the instance delete.
It should reflect the status without refresh.
This has been fixed back to OSP10.0. We will not backport further as it is a non-critical bug and is fixed in future releases.