ENG-4136: Add a state bit indicating whether or not a rejoining node
still has data and transactions (in the case of live rejoin)
outstanding.
ENG-4136: Pass the requestId string of the truncation snapshot which
completed to RealVoltDB.  Future use: figure out if the truncation
requested on rejoin is what completed.
ENG-4136: Add a request ID to the truncation snapshot request taken at
the end of rejoin.
ENG-4136: Only mark rejoin as fully done if we see the truncation
snapshot we requested when the data sync was done.  If we don't
request the same ID, it'll work eventually (we hope).