ENG-6057: Use the VoltTableRow method that preserves milliseconds when
converting to java.sql.Timestamp rather than old broken cowboy logic.
Merge pull request #1289 from VoltDB/eng6057

ENG-6057: Use the VoltTableRow method that preserves milliseconds when converting to java.sql.Timestamp rather than old broken cowboy logic.

r=rbetts (YES, RUN!)