Update yaml to work with latest version of vmdb2

[lpsinger]

• Update vmdb2 to master in order to fix errors like this:

  ERROR: No runner implements step with keys fs-type, start, mkpart, part-tag, end, device

• I found that I had to add a kpartx step, which was hinted at in the kpartx section in partition.mdwn:

  Create loop devices for partitions in an image file. Not needed when installing to a real block device, instead of an image file.

• I found from reading the source code that the part-tag and fs-tag keys had been renamed to tag, and so I updated the yaml file accordingly.

Fixes #47.

[gwolf]

Thank you very much for the contribution -- I have, however, just pulled in vmdb's author commits fixing this same issue, more or less in the same way :-)

[lpsinger]

Thanks, that worked!