Code review comment for lp:~schwann/gallery-app/gallery-pick-return

I have tested this on my device with Mir, and it does work fine. However I do think we should quit if gallery-app wasn't already running before getting called for picking. If a user didn't have gallery-app in their list of running apps, it would be annoying to leave it running after picking is complete. From the users point of view, they used system-settings to pick a background, not gallery-app. The fact that it's gallery-app doing the work, should be transparent to the user.