MODE-2298 Updated sequencers and text extractors to better handle the case when a repository has been shut down and there's still work being processed

The only problem with marking `shutdown=true` at the start of shutdown is that it really denotes that shutdown _has been requested_ rather than _shutdown has completed_, and it changes the behavior of `isShutdown()`. IOW, that method no longer provides a way for other components to know whether the sequencers have _completed_ their processing. Is this the new intent? Should the method be changed to something more appropriate, like `isShuttingDown()' ??