[1/3] Fix getVlanID() and getVlanDevice().

Previous implementations work only under root privileges.
This patch reimplements both functions to use "ip" tool.

Change-Id: Ieab0f44cf4c4f6f16f81435cb732ccacf57b0767
Signed-off-by: Amador Pahim <apahim@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/18180
Reviewed-by: Antoni Segura Puimedon <asegurap@redhat.com>
Reviewed-by: Dan Kenigsberg <danken@redhat.com>