This change adds the ability to boot Windows and Linux instances in XenServer using different sets of vm-params.  
This change adds the ability to boot Windows and Linux instances in XenServer using different sets of vm-params.  

Images in glance should have a property set with a key of `os_type` and a value of either `windows` or `linux`.  Images without `os_type` set default to `linux`.

Linux images boot para-virtualized, while Windows images boot via HVM.
n0ano/ganttclient