use atomic

cloud/src/recycler/recycler.cpp

@@ -1053,7 +1053,7 @@ int InstanceRecycler::recycle_versions() {
 int InstanceRecycler::recycle_tablets(int64_t table_id, int64_t index_id, int64_t partition_id,
                                       bool is_empty_tablet) {
     int num_scanned = 0;
-    int num_recycled = 0;
+    std::atomic_int num_recycled = 0;
 
     std::string tablet_key_begin, tablet_key_end;
     std::string stats_key_begin, stats_key_end;