Events indicating a changed Agent status should fire only for effective changes

Current Situation

If an Agent A1 is deployed but that cannot be coupled, for example if the host is not reachable, then an event is fired indicating that the Agent status changed.

This will result in frequent refresh of the "Resources->Agents" view and the "Manage Controller/Agents" view.

Desired Behavior

Events about a changed Agent status should be fired only if there is an effective status change..