Updated version of ubuntu base image.

Removed previous hashes because they may enter in conflict with the new version's hashes if they exist.
Signed-off-by: vimes <joaomares@gmail.com>
If the repository hashes change, they may enter in conflict with the hashes already present on the base image producing errors of the following kind: http://askubuntu.com/questions/41605/trouble-downloading-updates-due-to-a-hash-sum-mismatch-error