[VLAN]: Fix promiscous/allmulti synchronization races

The set_multicast_list function may be called without holding the rtnl
mutex, resulting in races when changing the underlying device's promiscous
and allmulti state. Use the change_rx_mode hook, which is always invoked
under the rtnl.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>