[TASK] Mitigate erroring builds

Builds error regularily because our scripts
need to output something at least every 10 minutes.

This might not happen as the complete functional test
suite takes longer than that.

To avoid these issues, only execute unit tests and lint
in parallel and each functional test suite.

By doing so, each functional test suite can take
up to 10 minutes which is for now a limit we do not
reach.

Releases: 6.2
Change-Id: I74cac706748cc03388f814f09e799a8705a26bca
now hopefully hhvm

Change-Id: Idd0bbdd5b13dd5b9fbb16a491d7dc08ffbdaedba