ENG-5318: Fix flaky snapshot test.

Return a success to the MPI even if the site has no snapshot work to do.
ENG-5598 better condition checking in TableStreamer notifyTupleDelete
Merge pull request #1054 from VoltDB/ENG-5598

ENG-5598 better condition checking in TableStreamer notifyTupleDelete
Merge pull request #1052 from VoltDB/ENG-5318

ENG-5318: Fix flaky snapshot test.
- Fix description of setversion task in build.xml
- Make sed on OSX happier change_version.sh
Update version string to 4.0.2.