selftests: forwarding: Add a test for VLAN deletion

[ Upstream commit 4fabf3bf ]

Add a VLAN on a bridge port, delete it and make sure the PVID VLAN is
not affected.

Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>