When not creating a core dump due to resource limits specifying

a maximum dump size of 0, return a size-related error, rather
than returning success.  Otherwise, waitpid() will incorrectly
return a status indicating that a core dump was created.  Note
that the specific error doesn't actually matter, since it's lost.

MFC after:	2 weeks
PR:		60367
Submitted by:	Valentin Nechayev <netch@netch.kiev.ua>

sys/kern/kern_sig.c

@@ -2555,7 +2555,7 @@ coredump(struct thread *td)
 	limit = p->p_rlimit[RLIMIT_CORE].rlim_cur;
 	if (limit == 0) {
 		PROC_UNLOCK(p);
-		return 0;
+		return EFBIG;
 	}
 	PROC_UNLOCK(p);