Confirm agent Shutdown

[AnarManafov]

When DDS commander starts its shutdown, it sends the shutdown command to all agents, but doesn't wait until they finish.
To make DDS more reliable, it should wait a certain amount of time until all agents disconnect. But it should drop the connection once the timeout is reached no matter what.

It should improve the cleaning processes, as plug-ins now shutdown RMS jobs after DDS commander is down, which might be too soon for some agents. Instead of introducing an artificial sleep before cancelling RMS jobs, DDS will relay on natural shutdown time of agents limited by the configurable time limit (timeout).