[TASK] Travis: Speedup cloning of repos

Make use of the additional parameters of git clone
to vastly reduce the amount of data transfered when cloning the
repositories.

Releases: 6.2, 6.1, 6.0, 4.7, 4.5
Change-Id: Id0c5f3a4ed7ee0bdeb6053c6e0dc606362909d1e
Reviewed-on: https://review.typo3.org/22058
Reviewed-by: Christian Kuhn
Tested-by: Christian Kuhn