Building OS images centos and ubuntu

Those images are supposed to be used for
image based provisioning. This patch set
needs python-imgcreate package to be available.

Implements: blueprint image-based-provisioning
Change-Id: I4f038c99d4caf7d2b6e291bff29572b3a45d92c7
Partial image script for ubuntu

Change-Id: I650052154fe7b483aaba89389e9a09f80fc1543e