[SPARK-3304] [YARN] ApplicationMaster's Finish status is wrong when uncaught exception is thrown from ReporterThread

I'm kind of on the edge of whether we should expose this to the normal user or not.  Generally I wouldn't expect this to need to be configured so I'm thinking we should leave it out of the docs and if we find users are actually setting it then expose it.  

Do you have objections to that or specific use cases where this needs to be configured?