Fix cache shutdown order (facebookincubator#10239)

Summary:
Currently, ssd cache shutdown happens after shard shutdown where entries are cleared. If there is any pending write, the ssd write will fail as the entry no longer exists. Therefore, the shutdown order needs to be reversed.

Pull Request resolved: facebookincubator#10239

Reviewed By: xiaoxmeng

Differential Revision: D58709223

Pulled By: zacw7

fbshipit-source-id: 56e61db69b08743004a99c93fd84006e5772cd63

velox/common/caching/AsyncDataCache.cpp

@@ -676,12 +676,12 @@ AsyncDataCache** AsyncDataCache::getInstancePtr() {
 }
 
 void AsyncDataCache::shutdown() {
-  for (auto& shard : shards_) {
-    shard->shutdown();
-  }
   if (ssdCache_) {
     ssdCache_->shutdown();
   }
+  for (auto& shard : shards_) {
+    shard->shutdown();
+  }
 }
 
 void CacheShard::shutdown() {