ENG-4730: Missed this bit when 'fixing' this issue as part of the MP
read-only optimizations.  Also need to go back and update the new
master set in any EveryPartitionTask that might be in the
MpTransactionTaskQueue's backlog.
Merge pull request #834 from VoltDB/eng4730

ENG-4730: Finish fix
r=jhugg
ENG-5111: Remove group support for export. Fix a bug.
Fixes a bug where on-server export crashes on startup if there is no export tables.
Merge remote-tracking branch 'origin/master' into ENG-5111-noexportclient