Fix global lock contention in DistClusterControllerStateModel caused by Optional.empty() singleton#3052

junkaixue merged 3 commits intoapache:masterapache/helix:masterfrom

LZD-PratyushBhatt:fix_global_lock_contentionLZD-PratyushBhatt/helix:fix_global_lock_contentionCopy head branch name to clipboard