Release all resources when shutting down an RPZ zone during an update

Release all resources when shutting down an RPZ zone during an update

If an RPZ zone is to be freed during an update, canceling the
update_quantum() event is not enough because the resources released when
an update completes also need to be accounted for.  Failure to do this
results in a hang upon shutdown.  Fix by copying cleanup code from the
end of update_quantum() to rpz_detach().