Remove unused main thread
For ENG-5588, take a stab at removing the check that is only supposed to run at startup
Merge pull request #1012 from VoltDB/ENG-5588

Eng 5588 Clean up random unused thread and fix issue with leader appointer failover startup checks being applied at runtime
Merge branch 'master' into ENG-5434
ENG-5434 addressed Andrew G. UI Comments