Fix typo in error message.
Fix typo in error message.

Change-Id: Ia5c8e70a9185f4feb7bb4c04170b1bb01c77d431

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