ISPN-5007 Enhance the distribution script to detect missing artifacts
ISPN-5008 7.0.x missing cachestore-remote and extended-statistics modules

Replace <fileset/> with <file/> to have the script fail when the source files are missing.
Fix missing cachestore-remote and extended-statistics modules.
ISPN-3938 AdvancedAsyncCacheLoader.process() concurrency issues

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