Use m-b-ssd-1 for m-b-1, set up disk if not already done

This uses mojo-builder-ssd-1 for mojo-builder-1 and formats +
creates the /ssd/docker directory if it doesn't already exist so
the script works properly after destroying and creating a new disk.
Merge pull request #10 from domokit/disk_improvements

Use m-b-ssd-1 for m-b-1, set up disk if not already done