The current code only allow netlink to reach the initial network namespace,
which caused trouble for any client running inside container.

This patch would make sure TCMU netlink would work for all network
namespaces.
Signed-off-by: NSheng Yang <sheng@yasker.org>
Acked-by: NAndy Grover <agrover@redhat.com>
Signed-off-by: NNicholas Bellinger <nab@linux-iscsi.org>