fix bug of worker exit (#4786)

Co-authored-by: oneflow-ci-bot <69100618+oneflow-ci-bot@users.noreply.github.com>

oneflow/core/job/cluster.cpp

@@ -83,7 +83,6 @@ Maybe<void> Cluster::WorkerLoop() {
     }
   }
   ClusterInstruction::HaltBarrier();
-  Global<EnvGlobalObjectsScope>::Delete();
   return Maybe<void>::Ok();
 }
 

oneflow/core/job/oneflow_worker.cpp

@@ -37,6 +37,7 @@ Maybe<void> Run(const std::string& env_proto_filepath) {
   Global<EnvGlobalObjectsScope>::SetAllocated(new EnvGlobalObjectsScope());
   JUST(Global<EnvGlobalObjectsScope>::Get()->Init(env_proto));
   JUST(Cluster::WorkerLoop());
+  Global<EnvGlobalObjectsScope>::Delete();
   return Maybe<void>::Ok();
 }