fix executor last task not clear

mindspore/ccsrc/backend/session/executor.cc

@@ -217,12 +217,17 @@ void Executor::OnEvent(const ExecutorEvent &event) {
   if (event == ExecutorEvent::kRunGraphFinished) {
     OnRunGraphFinished();
   } else if (event == ExecutorEvent::kClear) {
-    WorkerJoin();
+    OnClear();
   } else if (event == ExecutorEvent::kException) {
     OnException();
   }
 }
 
+void Executor::OnClear() {
+  WorkerJoin();
+  ClearDoneTasks();
+}
+
 void Executor::OnException() {
   std::vector<std::shared_ptr<Task>> new_done_tasks;
   {

mindspore/ccsrc/backend/session/executor.h

@@ -176,6 +176,7 @@ class Executor {
   bool IsTaskReady(const std::shared_ptr<RunGraphTask> &task);
   void WaitLockedInputs(const SessionPtr &session, const std::shared_ptr<RunGraphTask> &task);
   void OnWorkerExit();
+  void OnClear();
   void OnRunGraphFinished();
   void OnException();
   void ClearDoneTasks();