Fix bug of destroy_callback_list not cleared when thread mgr destroy (#844)

The destroy_callback_list variable in thread_manager_destroy is not cleared.
When wamr is started as a task, after exiting and restarting, it will loop
endlessly in traverse_list.

Signed-off-by: zhouliang3 <zhouliang3@xiaomi.com>

core/iwasm/libraries/thread-mgr/thread_manager.c

@@ -240,6 +240,7 @@ void
 wasm_cluster_cancel_all_callbacks()
 {
     traverse_list(destroy_callback_list, free_node_visitor, NULL);
+    bh_list_init(destroy_callback_list);
 }
 
 WASMCluster *