[LibOS] Fix the storage of local_objects leaks in shim_async_helper

before DkThreadExit(), allocated resource local_objects were not freed, causing resource leakage of local_objects content

Signed-off-by: Gary <gang1.wang@intel.com>

LibOS/shim/src/shim_async.c

@@ -281,6 +281,7 @@ update_list:
     unlock(async_helper_lock);
     put_thread(self);
     debug("async helper thread terminated\n");
+    free(local_objects);
 
     DkThreadExit();
 }