net/sched: act_tunnel_key: Fix double free dst_cache

dst_cache_destroy will be called in dst_release

dst_release-->dst_destroy_rcu-->dst_destroy-->metadata_dst_free
-->dst_cache_destroy

It should not call dst_cache_destroy before dst_release

Fixes: 41411e2f ("net/sched: act_tunnel_key: Add dst_cache support")
Signed-off-by: wenxu <wenxu@ucloud.cn>
Signed-off-by: David S. Miller <davem@davemloft.net>