Add a test for dependency of mcast_vlan_snooping on vlan_filtering. If
vlan_filtering gets disabled, then mcast_vlan_snooping must be
automatically disabled as well.

TEST: Disable multicast vlan snooping when vlan filtering is disabled   [ OK ]
Signed-off-by: Nikolay Aleksandrov <nikolay@nvidia.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>