nvme-cli/list-ns: fix identifying active or allocated namespaces list

nvme-cli/list-ns: fix identifying active or allocated namespaces list

The logic of the CNS field of identify namespace list is wrong.
For example, nvme list-ns /dev/nvme0 -n 0  should return active
namespaces list starting with id 1 (including), but currently this
script command returns INVALID_OPCODE if the target doesn't support
listing allocated namespaces or all the allocated attached namespaces
id. So fix it by swaping the CNS flags of active and allocated list.

Signed-off-by: Guan Junxiong <guanjunxiong@huawei.com>
Reviewed-by: Sagi Grimberg <sagi at grimberg.me>
Signed-off-by: Keith Busch <keith.busch@intel.com>