bridge: Do not send queries on multicast group leaves

As it stands the bridge IGMP snooping system will respond to
group leave messages with queries for remaining membership.
This is both unnecessary and undesirable.  First of all any
multicast routers present should be doing this rather than us.
What's more the queries that we send may end up upsetting other
multicast snooping swithces in the system that are buggy.

In fact, we can simply remove the code that send these queries
because the existing membership expiry mechanism doesn't rely
on them anyway.

So this patch simply removes all code associated with group
queries in response to group leave messages.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>