Disable the TestGraphHandler.java class for maven unit tests as it is failing in the travis ci builds due failed lookups of the gnuplot scripts in the class path.
Disable the TestGraphHandler.java class for maven unit tests as it is
failing in the travis ci builds due failed lookups of the gnuplot
scripts in the class path.

Signed-off-by: Chris Larsen <83037b211e1d109d6858769a113e269c3139ffd3@yahoo-inc.com>

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