Create a new baremetal element
Create a new baremetal element

Rather than using a script to mount the image using nbd to extract the
kernel and ramdisk, make a new element called baremetal, which contains
a cleanup.d script that will copy them out to <image name>.{vmlinuz,initrd}.

Closes-Bug: 1224669
Change-Id: I8f3569aa12148d18b1c8242b6fbbd8857894b26f

citrix-openstack-build/dib-utils,openstack/dib-utils,openstack/dib-utils,citrix-openstack-build/dib-utils