[baremetal] Switch VCP base image to UCA

[baremetal] Switch VCP base image to UCA

Since Mirantis prebuilt image comes with salt-minion 2016.3 instead
of 2016.11 and upgrading it leads to a hard to break catch-22, use
the Ubuntu cloud archive image we already download for FN VMs and
pre-install:
- a newer kernel (hwe-edge);
- salt-minion (2016.11);
This also implicitly aligns the image handling on AArch64 and x86_64.

Change-Id: I86d1c777449d37bdd0348936a598e3ffe9d265af
Signed-off-by: Alexandru Avadanii <Alexandru.Avadanii@enea.com>