Bumping gaia.json for 1 gaia revision(s) a=gaia-bump

========

https://hg.mozilla.org/integration/gaia-central/rev/8561b70fb9d7
Author: Julien Wajsberg <felash@gmail.com>
Desc: Bug 1021706 - [Marionette-js-runner] have several jobs to run marionette js tests r=jlal
Bumping manifests a=b2g-bump