Dynamically compute how many rows to flush per iteration.
Dynamically compute how many rows to flush per iteration.

This ensures that we flush more aggressively when under pressure.

Change-Id: Ie82f93b080e1841b560e6a34a288cda9e755f65e

MadDogTechnology/opentsdb,MadDogTechnology/opentsdb,sidhhu/opentsdb,kidaa/opentsdb,ShefronYudy/opentsdb,andyflury/opentsdb,OpenTSDB/opentsdb,ShefronYudy/opentsdb,johann8384/opentsdb,MadDogTechnology/opentsdb,kidaa/opentsdb,alienth/opentsdb,andyflury/opentsdb,OpenTSDB/opentsdb,johann8384/opentsdb,alienth/opentsdb,sidhhu/opentsdb,OpenTSDB/opentsdb,eswdd/opentsdb,eswdd/opentsdb