Support vnic_type in OS::Neutron::Port

This commit adds support for vnic_type
in OS::Neutron::Port. vnic_tpes can be
normal, direct, and macvtap

Change-Id: If7498c69abb44fa1ee7ed8bed15a221ca9aea313
Implements: blueprint neutron-resource-add-pci-port
Merge "Support vnic_type in OS::Neutron::Port"