location-service needs to provide an Autopilot helper for apps to disable the prompt

[Brendan Donegan]

Some apps that use the location service prompt for the user to accept the permission. This often interferes with testing so we need to provide a way for apps to disable or automatically accept this prompt so that they can run tests unimpeded. An example solution was already done in Clock by setting the property custom.location.testing to True and restarting the location service: https://code.launchpad.net/~brendan-donegan/ubuntu-clock-app/disable_location_prompt/+merge/242682, although any solution which either disables or automatically accepts the prompt would be accepted. Bonus points for allowing it to be rejected as well.