VMs with hardcoded platform network devices are forced to use old
style '-net nic' command line config. Current we use qemu's vlan
option to hook this with the '-netdev' host side of things.

However since qemu 1.2 there is '-net nic,netdev=X' option for
explicitly referencing a netdev ID, which is more inline with
typical VM commandlines, so let's switch to that
Signed-off-by: NCole Robinson <crobinso@redhat.com>