[TASK] Mitigate risk for travis-ci timeouts

Not using --keep-order in parallel gives output as soon as a
job is finished and thus reduces the risk for travis-ci timeouts.

Change-Id: If33087fbf4fc2b927ce52d153625140d89c2603a
Releases: 6.2
Reviewed-on: https://review.typo3.org/29553
Reviewed-by: Wouter Wolters
Reviewed-by: Philipp Gampe
Tested-by: Philipp Gampe
Reviewed-by: Stefan Neufeind
Reviewed-by: Helmut Hummel
Tested-by: Helmut Hummel