Revert "Downgrade ubuntu to v12.04"

This reverts commit 3f46f809f4a3190c91bfc95387131999c125576f.
Revert "Downgrade ubuntu to v14.04"

This reverts commit 97868cafa99b090c0ddeb3156b37cf29440e7d17.
Revert "Revert back to base image Ubuntu"

This reverts commit 813079e64252d1c60978f875ea7f68ba8fc3daca.