ipv6: use call_rcu_hurry() in fib6_info_release()

This is a followup of commit c4e86b43 ("net: add two more
call_rcu_hurry()")

fib6_info_destroy_rcu() is calling nexthop_put() or fib6_nh_release()

We must not delay it too much or risk unregister_netdevice/ref_tracker
traces because references to netdev are not released in time.

This should speedup device/netns dismantles when CONFIG_RCU_LAZY=y

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>