Add mkfs to the baremetal-deploy-helper rootwrap

The nova-baremetal-deploy-helper uses the mkfs command to
format the ephemeral partition (if configured). The
command works today because it is also defined in the
compute.filters file but we should be explicit here.

Change-Id: I79c31ffd26ff92d35d3d9836f2a8954a9a07c2c0
Merge "Add mkfs to the baremetal-deploy-helper rootwrap"