network: better validation of devices in hostdev network pool

network: better validation of devices in hostdev network pool

This adds a few validations to the devices listed for a hostdev network:

* devices must be listed by PCI address, not by netdev name

* listing a device by PCI address is valid only for hostdev networks, not
  for other types of network (e.g. macvtap passthrough).

* each device in a hostdev pool must be an SR-IOV VF

Resolves: https://bugzilla.redhat.com/1004676