bridge: don't try to update timers in case of broken MLD queries

Currently we are reading an uninitialized value for the max_delay
variable when snooping an MLD query message of invalid length and would
update our timers with that.

Fixing this by simply ignoring such broken MLD queries (just like we do
for IGMP already).

This is a regression introduced by:
"bridge: disable snooping if there is no querier" (b00589af)

Reported-by: Paul Bolle <pebolle@tiscali.nl>
Signed-off-by: Linus Lüssing <linus.luessing@web.de>
Signed-off-by: David S. Miller <davem@davemloft.net>