In case of HA routers IPv6 forwarding is not disabled by default and
then enabled only on master node.
Before this patch it was done in opposite way, so forwarding was
enabled by default and then disabled on backup nodes.
When forwarding was enabled/disabled for qg- port, MLDv2 packets are
sent and that might lead to temportary packets loss as packets to
FIP were sent to this backup node instead of master one.
(cherry picked from commit