should_not_sleep checks detect sleeps in calls from spawn blocks

Not sure of all the cases, but at least this one seems to detect the proc as sleeping:
```
/proc/foo()
	SHOULD_NOT_SLEEP(TRUE)
	spawn()
		bar()

/proc/bar()
	sleep(1)
```

Don't know if this is intended, but seems inconsistent when compared to handling of `set waitfor = FALSE`.