Only recalculate total_staged in getwork thread if required.

cgminer.c

@@ -3067,9 +3067,10 @@ static void *getwork_thread(void __maybe_unused *userdata)
 			lagging = true;
 
 		/* Wait until hash_pop tells us we need to create more work */
-		if (ts > opt_queue)
+		if (ts > opt_queue) {
 			pthread_cond_wait(&gws_cond, stgd_lock);
 			ts = __total_staged();
+		}
 		mutex_unlock(stgd_lock);
 		if (ts > opt_queue)
 			continue;