ENG-5759: Dont delete export overflow for rejoin. Let generation roll drain the old data.
ENG-5759: delete the unused method as well.
Merge branch 'master' into ENG-5759
ENG-5759: fix mkdir check for rejoin.
Merge branch 'master' into ENG-5759
ENG-5759: remove unused import
Merge branch 'master' into ENG-5759
Merge pull request #1100 from VoltDB/ENG-5759

ENG-5759: Dont delete export overflow for rejoin. Let generation roll dr...