[Merge] livecd-rootfs:uc18-kassel into livecd-rootfs:ubuntu/master

[Chih-Hsyuan Ho]

To Lukasz and Steve's comments on the decision of not having a model assertion created at the beginning, the fact is that it was never in our plan to host the image like this and customer(Intel) made this request after we delivered the final image. 

Actually, if it's beneficial in the long run, I am open to make necessary changes to the image to get it complied with any policy set up by your team as long as it is not too resource consuming. I will check with the project team on that. 
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https://code.launchpad.net/~ubuntu-core-dev/livecd-rootfs/+git/livecd-rootfs/+merge/366327
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