illustrates that line 62 in ExecutorServiceUtil will never be reached
removed awaitTermination and related noise from ExecutorServiceUtil

ExecutorService.shutdownNow returns the list of jobs that never
executed, not the list of jobs that didn't terminate.
added missing final in from what should have been a constant
removed unneeded parameter after ExecutorServiceUtil refactoring
removed unused constant
removed references to removed constant
Merge remote-tracking branch 'origin/master' into LOGBACK-848