bug engine: fix engine stop race

commit_hash:658bb8acfbc7cf1f3de9bba98b3851dbf4b96a91

Author: segoon

core/src/engine/plugin_manager.hpp

@@ -19,6 +19,12 @@ class PluginManager final {
         : mutex_set_(tp, worker_count)
     {}
 
+    ~PluginManager()
+    {
+        // Wait until all Hook*() are finished
+        (void)mutex_set_.WriteLock();
+    }
+
     void RegisterPlugin(PluginBase& plugin) {
         has_any_plugin_ = true;