Signed-off-by: Nganlan <tony.gan@huawei.com>

Need one interface to get dlns, and can set default parent for new namespace. add dlns_create2 interface which caller can create namespace without inherit
from default namespace.

test: creat2 without flags
Signed-off-by: Nhuanghuijin <huanghuijin@huawei.com>

Signed-off-by: Nwangjiahui <wangjiahui27@huawei.com>

Signed-off-by: Nwangjiahui <wangjiahui27@huawei.com>