IPv6: Fix not join all-router mcast group when forwarding set.
IPv6: Fix not join all-router mcast group when forwarding set.

When forwarding was set and a new net device is register,
we need add this device to the all-router mcast group.

Signed-off-by: Li Wei <b1e2e3ae26f1849f6f819475f53ed1fe23965c50@cn.fujitsu.com>
Signed-off-by: David S. Miller <fe08d3c717adf2ae63592e4c9aec6e3e404d8e3e@davemloft.net>

KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas