Installing an updated deb file fails

[vaslabs]

Reproduce:

1. Install 0.7.0
2. Install 0.7.1

Workaround:
Since we don't have any configuration yet that needs to persist across updates it is safe to uninstall and then install again

apt-get remove piwebagent2
dpkg -i ./<new_package>.deb

[vaslabs]

probably the pre/post installation scripts mess up the update, will make them less error prone

[vaslabs]

This is because we don't actually follow the dpkg flow, which passes an argument to the scripts to tell us if it's an upgrade. need to have a review on those