ip: fib_rules: Fetch net from fib_rule in fib[46]_rule_configure().

The following patch will not set skb->sk from VRF path.

Let's fetch net from fib_rule->fr_net instead of sock_net(skb->sk)
in fib[46]_rule_configure().

Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Tested-by: Ido Schimmel <idosch@nvidia.com>
Link: https://patch.msgid.link/20250207072502.87775-5-kuniyu@amazon.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>