/tmp is not very secure. But the real reason is so that we can
re-run the setup script again should things fail.
/home/yellowtent/box/scripts/installer.sh --data-file /root/cloudron-update-data.json
This redesigns how update works. installer.sh now rebuild the package,
stops the old code and starts the new code. Importantly, it does not
download the new package, this is left to the caller. cloudron-setup
downloads the code and calls installer.sh of the downloaded code.
Same goes for updater.sh. This means that installer.sh itself is now
easily updatable.
Part of #152
This ensures it can start and stop the box process.
Due to control-group setting to killall children
the updater itself would get killed if the box service
restarts