center restart with new shm; set center node ssn.

lichao

2021-06-02 993c556000a414011626770540678948f16eaa9e

 src/exported_symbols

@@ -5,6 +5,7 @@
   BHUnregister;
   BHRegisterTopics;
   BHQueryTopicAddress;
   BHQueryProcs;
   BHSubscribeTopics;
   BHStartWorker;
   BHHeartbeatEasy;