More test coverage for incremental stats

Change-Id: I17778dcf019c2a219baa678211f221b7e04813bb
Reviewed-on: http://gerrit.sjc.cloudera.com:8080/5446
Reviewed-by: Alex Behm <alex.behm@cloudera.com>
Tested-by: jenkins
(cherry picked from commit 2f5ec47e0b5dd26bc9dfe884481d3a316201be2d)
Reviewed-on: http://gerrit.sjc.cloudera.com:8080/5460
Reviewed-by: Henry Robinson <henry@cloudera.com>