RFC2710 says:
1) MLD messages are never sent for multicast addresses whose scope is 0
   (reserved) or 1 (node-local).
2) MLD messages ARE sent for multicast addresses whose scope is 2
   (link-local), including Solicited-Node multicast addersses [ADDR-ARCH],
   except for the link-scope, all-nodes address (FF02::1).

      The current MLDv1 code does not send reports for link-scope addresses
and doesn't restrict scope 0. This may break switches that snoop reports for
determining which ports should receive particular addresses.  Patch below.