SUNRPC: Replace flush_workqueue() with cancel_work_sync() and friends

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

net/sunrpc/cache.c

@@ -371,8 +371,7 @@ int cache_unregister(struct cache_detail *cd)
 	}
 	if (list_empty(&cache_list)) {
 		/* module must be being unloaded so its safe to kill the worker */
-		cancel_delayed_work(&cache_cleaner);
-		flush_scheduled_work();
+		cancel_delayed_work_sync(&cache_cleaner);
 	}
 	return 0;
 }