Comment 17 for bug 1709710

I've force-pushed to collab/gmcharlt/lp1709710-smarter-chunk-length a final set of patches:

- a further cleaned-up version of Mike's patch that ensures that the final completion status message and fixes const correctness and makes whitespace match local conventions
- a unit test

http://git.evergreen-ils.org/?p=working/OpenSRF.git;a=shortlog;h=refs/heads/collab/gmcharlt/lp1709710-smarter-chunk-length