Remove apt-get upgrade

[hamiltont]

Currently upgrade breaks the container build. Upgrading is unrecommended inside a container, as there is no init system and some packages have to be held back.

To see the official issue: https://github.com/dotcloud/docker/issues/1724 To see workarounds: https://github.com/racker/docker-ubuntu-with-updates/blob/master/precise/Dockerfile

[hamiltont]

AFAIK, upgrade will sometimes work fine and sometimes not work fine, depending on the current status of ubuntu:latest. As of me writing this, it is not working