Don't set password for user 'fbx'

Created by: SunilMohanAdapa

The 'fbx' user will have password disabled by default. This is only a problem for users who want to login on console before Plinth can create an administrative user during first boot. This only happens when Plinth is not accessible due to various reasons. While we continue to fix problems that will make Plinth a reliable option, our fallback option is to use a password setting tool on the downloaded image.

The password setting tool will loop mount the image and set a password inside the image for the 'fbx' user. This is, for now, a command line tool that requires some knowledge of UNIX command line. However, if the users are wishing to login to shell as 'fbx' user, so is that process.

Essentially, in the normal flow, users won't need 'fbx' user and will use the first boot user create by Plinth. When Plinth is not accessible and debugging needs to be done, users will run the password setting tool on the image and then use the image.

TODO: Remove the 'fbx' user altogether. Currently this is not done because the password setting tool can't create users and wants to have minimal dependencies to work from many OSes/distributions.