netfilter: ipvs: make global sysctl readonly in non-init netns

netfilter: ipvs: make global sysctl readonly in non-init netns

[ Upstream commit c4441b1d16e2775e26ef7a3004d40e30196b76b2 ]

Because the data pointer of net/ipv4/vs/debug_level is not updated per
netns, it must be marked as read-only in non-init netns.

Fixes: 9f010cc4336e ("IPVS: netns, final patch enabling network name space.")
Signed-off-by: Antoine Tenart <atenart@kernel.org>
Acked-by: Julian Anastasov <ja@ssi.bg>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>