Helper APIs are needed to

 - Populate basic virNetworkPortDef from virDomainNetDef
 - Set a virDomainActualNetDef from virNetworkPortDef
 - Populate a full virNetworkPortDef from virDomainActualNetDef
Reviewed-by: NLaine Stump <laine@laine.org>
Signed-off-by: NDaniel P. Berrangé <berrange@redhat.com>