[master] 1b606ff94 ci: Increase parallelism in Travis CI builds

[Dridi Boukelmoune]

On Wed, Oct 28, 2020 at 3:27 PM Dridi Boukelmoune
<dridi.boukelmoune at gmail.com> wrote:
>
>
> commit 1b606ff940309d3ba62a392ac3050902aa740b8c
> Author: Dridi Boukelmoune <dridi.boukelmoune at gmail.com>
> Date:   Wed Oct 28 16:21:38 2020 +0100
>
>     ci: Increase parallelism in Travis CI builds
>
>     They are taking too long, needlessly holding onto job slots forever.

We saved 10 minutes per build (a couple minutes per job). But I think
most of the time is wasted waiting for and booting VMs instead of
container builds...