Trust prompt doesn't use translations at the first run

Can you explain the steps more clearly - you flash the phone, boot, change language, reboot, and trust prompts are not in the right language?

@Pat: Flash the phone, then in the setup wizard you need to change language to Hungarian, then start an app (for instance Weather App), the trust prompt is in English. Reboot the phone, start another app (uNav), the trust prompt is in the right language.

This is not the same bug: https://bugs.launchpad.net/canonical-devices-system-image/+bug/1582169
I guess the main reason behind that bug is that these strings don't included in the .pot file.

Translations are not provided by the trust-store in the general case. It relies on the respective services providing them, and on the runtime language setup. I think we are seeing a race here as the trust-store instances are started up prior to the language being chosen in the wizard. So we either start supporting changes to the language selection at runtime or postpone startup of the trust-store until after the wizard.

After the user pick up the language from Welcome Wizard, unity8 sends out a few signals and restart some services. It includes

- org.freedesktop.DBus UpdateActivationEnvironment (LANGUAGE, LANG, LC_ALL)
- initctl set-env --global
- restarting maliit-server, indicator-messages, unity8-dash, indicator-services-end, indicator-services-start.

There are a few approaches to fix
- add a few more initctl restart to restart cameraservice-trust-stored, pay-service-trust-stored, pulseaudio-trust-stored, ubuntu-location-service-trust-stored.
- send yet another upstart signals
- restart trust-store daemons, when unity8-dash or maliit, indicator-messages restarted.
- reuse the indicator-services-end & indicator-services-start upstart event, and restart trust-store daemons.

I propose to use indicator-services-end & indicator-services-start upstart event to restart trust-store daemons.

Based on the idea of using indicator-services-end & indicator-services-start upstart event.

changes need to be done in
ubuntu-touch-session: /usr/share/upstart/sessions/cameraservice-trust-stored.conf
ubuntu-touch-session: /usr/share/upstart/sessions/pulseaudio-trust-stored.conf
ubuntu-location-service-bin: /usr/share/upstart/sessions/ubuntu-location-service-trust-stored.conf
pay-service: /usr/share/upstart/sessions/pay-service-trust-stored.conf

* Bileto Landing Tickets - https://requests.ci-train.ubuntu.com/#/ticket/1652
* Merge into trunk : lp1582148 : Code : location-service - https://code.launchpad.net/~chihchun/location-service/lp1582148/+merge/299553
* Merge into trunk : lp1582148 : Code : Ubuntu Touch session manager - https://code.launchpad.net/~chihchun/ubuntu-touch-session/lp1582148/+merge/299551

The other merge request is still requiring top approval and the ticket hasn't landed yet therefore.