Added instructions for VLANs on Mellanox switch

Partial-Bug: 1359216
Change-Id: I30f4590354a5cbdab51b3047ef3bbf433d47980f
Signed-off-by: Aviram Bar-Haim <aviramb@mellanox.com>
Merge "Added instructions for VLANs on Mellanox switch"