ENG-5793: Add checks to the RestoreAgent that, on recover, verify that
we find table data files for all of the tables listed in the snapshot
digest.  Also, generate a useful failure message when this failure
occurs, rather than generating a cryptic message about missing the
catalog.
Merge pull request #1249 from VoltDB/eng5793

ENG-5793: Add checks to the RestoreAgent that, on recover, verify that