HG examples: Possible data races

[ryancaicse]

Hi, should thread-shared static variable hg_progress_shutdown_flag be protected by locks?

https://github.com/mercury-hpc/mercury/blob/ce847b771def57e9d63f33313ed81149b366648b/Examples/src/example_rpc_engine.c#L50-L63

https://github.com/mercury-hpc/mercury/blob/ce847b771def57e9d63f33313ed81149b366648b/Examples/src/example_rpc_engine.c#L66-L84

[soumagne]

Yes you're right sorry, that's been low-priority for me on my list but that should be fixed to either use an atomic variable or use a lock.