Bumping gaia.json for 2 gaia-central revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/96f86ed3a99c
Author: Julien Wajsberg <felash@gmail.com>
Desc: Merge pull request #14362 from julienw/makefile-install-gaia-changes

Bug 946213 - [builds] Kill the app after flashing r=ochameau

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https://hg.mozilla.org/integration/gaia-central/rev/81d8da39af5d
Author: Julien Wajsberg <felash@gmail.com>
Desc: Bug 946213 - [builds] Kill the app after flashing r=ochameau

* kill the flashed app after flashing
* use a target-scoped var for TARGET_FOLDER
* use non-recursive vars for APP_NAME and APP_PID, because they're used at
  several places and it makes no sense to run them each time