Revert "Work is checked if it's stale elsewhere outside of can_roll so there is no need to check it again."

This reverts commit 5ad58f9a5ce1a6b99f3011e1811fa01040d12aa2.

cgminer.c

@@ -3648,7 +3648,8 @@ static inline bool should_roll(struct work *work)
  * reject blocks as invalid. */
 static inline bool can_roll(struct work *work)
 {
-	return (work->pool && work->rolltime && !work->clone && work->rolls < 7000);
+	return (work->pool && work->rolltime && !work->clone &&
+		work->rolls < 7000 && !stale_work(work, false));
 }
 
 static void roll_work(struct work *work)