Steps to reproduce:
Shut down the capture agent, which should be sending a "shutting_down" agent state. At least, this state is the only non-online state recognized by the capture admin service.
In the capture agent ui, the agent is listed as "shutting_down" with no icon, while agents that have not been seen in a while will get an "offline" status with an appropriate icon.
Agents that have shut down properly (and reported that to the core using the implemented status "shutting_down") should be shown as "offline" as well.