CLEANUP: tasks: use the local state, not t->state, to check for tasklets

CLEANUP: tasks: use the local state, not t->state, to check for tasklets

There's no point reading t->state to check for a tasklet after we've
atomically read the state into the local "state" variable. Not only it's
more expensive, it's also less clear whether that state is supposed to
be atomic or not. And in any case, tasks and tasklets have their type
forever and the one reflected in state is correct and stable.