ISPN-4643 Make sure EntryIterator doesn't return expired entries
ISPN-4821 RHQ operation 'Upload Proto Schemas' no longer works due to changes introduced by ISPN-4357
ISPN-3938 AdvancedAsyncCacheLoader.process() concurrency issues

Simplify ExecutorAllCompletionService to track the tasks itself instead of
using an ExecutorCompletionService.