ModClusterService stop commands are always draining sessions

Using the ModClusterService stop or stopContext commands via CLI always fails to move a context to the STOPPED state after failing to drain the active sessions. So these commands then aren't very useful for quickly stopping the context when desired if you can't do it without draining.

I think it'd make sense for any draining done by manual stops to also follow the session draining strategy used by typical stops from undeploy events.