selftests: bonding: create directly devices in the target namespaces

If failed to set link1_1 to netns client, we should delete link1_1 in the
cleanup path. But if set link1_1 to netns client successfully, delete
link1_1 will report warning. So it will be safer creating directly the
devices in the target namespaces.

Reported-by: Hangbin Liu <liuhangbin@gmail.com>
Closes: https://lore.kernel.org/all/ZNyJx1HtXaUzOkNA@Laptop-X1/


Signed-off-by: Zhengchao Shao <shaozhengchao@huawei.com>
Acked-by: Hangbin Liu <liuhangbin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>