stale running instances are going into limbo on redefs
caused by recompiling namespaces with defstates, tn/refresh, tn/refresh-all, etc.
cleaning those stale instances with their stop functions before redefining their states
In case a state does not have a :stop function, mount would (!) assume that
nothing needs to be cleaned on stop and will intern convert this state
to mount.NotStartedState on (mount/stop)
