scollector: Send hypervisor as metadata for vms

For example:
2014/12/16 15:00:40 info: metadata.go:128: AddMeta for /host=den-av01/hypervisor: den-vm01
2014/12/16 15:00:40 info: metadata.go:128: AddMeta for /host=den-dhcp01/hypervisor: den-vm01
I don't trust the order of the properties (r.Props). This ensures that name is is know before I get the runtimehost and create the metadata