restapi: [Fix] Add sPAPR VLAN in the REST API

This patch introduces support for using sPAPR VLAN in the REST API
when creating or updating NICs

Change-Id: I40a273c01247ee52b3f02671b48a35f387abbb88
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1069765
Signed-off-by: Gustavo Pedrosa <gustavo.pedrosa@eldorado.org.br>