zebra: Fix bug in netconf handling where dplane would drop the change

zebra: Fix bug in netconf handling where dplane would drop the change

When reading a on the fly change of an interested netconf netlink
message. The ifindex and ns_id for the context was being set for the sub structure
but not for the main context data structure and zebra_if_dplane_result
was dropping the result on the floor because it was expecting the ns_id and
the interface id to be in a different spot.

Signed-off-by: Donald Sharp <sharpd@nvidia.com>