Execute a callback for every complete DB traversal
Execute a callback for every complete DB traversal

This ensures that we don't enter a receive statement waiting for new DB
updates without first flushing the buffer.

COUCHDB-2724

fkaempfer/couchdb,fkaempfer/couchdb,fkaempfer/couchdb,fkaempfer/couchdb,fkaempfer/couchdb,fkaempfer/couchdb