Remove discarded work from quota used.

cgminer.c

@@ -3911,6 +3911,7 @@ void discard_work(struct work *work)
 	if (!work->clone && !work->rolls && !work->mined) {
 		if (work->pool) {
 			work->pool->discarded_work++;
+			work->pool->quota_used--;
 			work->pool->works--;
 		}
 		total_discarded++;