Use older Travis image
Use older Travis image

The Travis builds hang on TestHiveTableStatistics with the new images.

https://blog.travis-ci.com/2017-06-21-trusty-updates-2017-Q2-launch

troels/nz-presto,troels/nz-presto,troels/nz-presto,troels/nz-presto,troels/nz-presto