Allow version number that start with a v

Change-Id: I87b7ce92c7136aa3287639da411d74f681ebe4e3
Added -updates repositories to package build envs

This is why libvirt was unable to build in our existing build
environments.

Change-Id: I0a747cd4167833cab7c4e54e603f161f15e3e7db
Use NeCTAR trusty mirror

Change-Id: I5397bfec543240d451de814b9b4e36fe5a909014