tests: addNetwork with one or more vlans.

Added a couple of functional tests:

* testAddNetworkManyVlans
* testAddNetworkVlan

covering the behaviour related to addNetwork using vlans.

Change-Id: I0de5f07bf93fbffca11abce000217c5155177e77
Signed-off-by: Giuseppe Vallarelli <gvallare@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/17376
Reviewed-by: Antoni Segura Puimedon <asegurap@redhat.com>
Reviewed-by: Dan Kenigsberg <danken@redhat.com>