ENG-6767: DR replica - fix up logic for snapshot coordination, and initial k-safety work
ENG-6767: Some fixes for replica cluster rejoin, and make cluster die if a node fails during sync snapshot
ENG-6767: No more LeaderCache in AgentReceiver
Merge pull request #1647 from VoltDB/ENG-6767

ENG-6767: DR replica - fix up logic for snapshot coordination, and initi...