Study and refactor entrypoint_image according to different use cases

Created by: LuisAlejandro

As discussed in #130 (closed), currently the /entrypoint_image script outputs the following error when being executed inside the build script of vauxoo/odoo-80-image-shippable-auto:

sed: can't read /root/*/openerp/cli/server.py: No such file or directory

This is because the script expects the odoo codebase to be in /root and not in /.repo_requirements. The script should be adapted to run both on test and build environments.