Agent widget in Dashboard should be updated on change of cluster status

Current Situation

If the cluster status of a Controller cluster changes then the Agent widget is not updated.

Desired Behavior

If the cluster status of a Controller cluster changes, the Agent widget should be updated. The corresponding events are

• ProxyCoupled
• ProxyDecoupled

As a result, the Agent Status widget is updated for the following events

• AgentStateChanged
• ProxyCoupled
• ProxyDecoupled
• ItemAdded (with "objectType": "AGENT")
• ItemDeleted (with "objectType": "AGENT")
• ItemChanged (with "objectType": "AGENT")