Removing class option from machine metadata


<a href="https://github.gds/garimasingh">garimasingh</a>:
`class` option which was passed as a machine metadata via json, isn't
used anymore. Hence removing its reference from code.

<em><a href="https://github.gds/gds/vcloud-box-configurator/issues/6">Original issue</a> (gds/vcloud-box-configurator#6) created at 2013-08-09T13:22:06Z.</em>