hv_xen: generate correct type for paravirtualized nic (#57)
hv_xen: generate correct type for paravirtualized nic (#57)

With debian stretch (ganeti 2.15 and xen 4.8) the configuration file 
generated by ganeti is not correct, type=vif should be specified instead of
type=paravirtualized when using paravirtual nics.

Reviewed-by: Federico Morg Pareschi <ff862f58af48d157b995cd83870fbfa4aec8edf3@google.com>
yiannist/ganeti,mbakke/ganeti,yiannist/ganeti,mbakke/ganeti,ganeti/ganeti,mbakke/ganeti,ganeti/ganeti,yiannist/ganeti,ganeti/ganeti