ipvs: Fix use-after-free in ip_vs_in

hulk inclusion
category: bugfix
bugzilla: 15741
CVE: NA

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while unregistering ipvs module, ops_free_list calls
nf_unregister_net_hooks to do cleanup ipvs resource,
it need a RCU period. Howerver ip_vs_in is still hooked
the LOCALOUT chain, which dereference freed ipvs pointer
triggers use-after-free.

Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Reviewed-by: Mao Wenan <maowenan@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>