[PATCH] bonding: replicate IGMP traffic in activebackup mode

Replicate IGMP frames across all slaves in activebackup mode. This
ensures fail-over is rapid for multicast traffic as well. Otherwise,
multicast traffic will be lost until the next IGMP membership report
poll timeout.

This is conceptually similar to the treatment of IGMP traffic in
bond_alb_xmit. In that case, IGMP traffic transmitted on any slave
is re-routed to the active slave in order to ensure that multicast
traffic continues to be directed to the active receiver.

Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: Jeff Garzik <jgarzik@pobox.com>