[libvirt] [PATCH] macvtap IFF_VNET_HDR configuration

This patch sets or unsets the IFF_VNET_HDR flag depending on what device is used in the VM. The manipulation of the flag is done in the open function and is only fatal if the IFF_VNET_HDR flag could not be cleared although it has to be (or if an ioctl generally fails). In that case the macvtap tap is closed again and the macvtap interface torn. This patch also passes 'make syntax-check' :-). Signed-off-by: Stefan Berger <stefanb@us.ibm.com>