Make nova compute deployable on SLE12

This change makes Nova Compute deployable on SLES 12 and Chef 11
The correct path would be ```templates/suse-12.0```. But putting templates there would mean that things start to get messy once we want to support SLE12-SP1 (```templates/suse-12.1```). There are other possiblities to use different templates for differnt platforms as well, though. E.g. setting ```source``` based on ```platform_version```. (I'd probably prefer that in this special case)

Anyways, the current grep/sed construct is somewhat broken, it causes libvirtd restart with every chef-client run. I'll check if there is a simple fix for that. Otherwise I'll go down the template route.