At the moment LifecycleEvent.REMOVED is executed in either
CANCELLED_to_REMOVED or REMOVING_to_REMOVED transition.
The problem is LifecycleListener is executed together with
RemoveTask and in bad timings it may happen that
LifecycleListener notifies user about controller was removed
while it still may be available via the container registry.
It is necessary that this LifecycleEvent.REMOVED is being
sent when controller is removed from registry (i.e. RemoveTask
finished its execution).