block device(bdev) can be deleted before deleting namespace under subsystem created from the same.

[sunilkumarn417]

Able to delete the block device without removing the namespace created from same bdev.

[root@ceph-2sunilkumar-20z9ez-node6 ~]# podman run -it quay.io/ceph/nvmeof-cli:0.0.3 --server-address 10.0.210.84 --server-port 5500 get_subsystems
INFO:__main__:Get subsystems:
[
    {
        "nqn": "nqn.2014-08.org.nvmexpress.discovery",
        "subtype": "Discovery",
        "listen_addresses": [],
        "allow_any_host": true,
        "hosts": []
    },
    {
        "nqn": "nqn.2016-06.io.spdk:cnode1",
        "subtype": "NVMe",
        "listen_addresses": [],
        "allow_any_host": false,
        "hosts": [],
        "serial_number": "1",
        "model_number": "SPDK bdev Controller",
        "max_namespaces": 32,
        "min_cntlid": 1,
        "max_cntlid": 65519,
        "namespaces": [
            {
                "nsid": 1,
                "bdev_name": "bdev1",
                "name": "bdev1",
                "nguid": "45738EC4206D44DF923477C8089D874F",
                "uuid": "45738ec4-206d-44df-9234-77c8089d874f"
            }
        ]
    }
]

[root@ceph-2sunilkumar-20z9ez-node6 ~]# podman run -it quay.io/ceph/nvmeof-cli:0.0.3 --server-address 10.0.210.84 --server-port 5500 delete_bdev -b bdev1
INFO:__main__:Deleted bdev bdev1: True

[root@ceph-2sunilkumar-20z9ez-node6 ~]# podman run -it quay.io/ceph/nvmeof-cli:0.0.3 --server-address 10.0.210.84 --server-port 5500 get_subsystems
INFO:__main__:Get subsystems:
[
    {
        "nqn": "nqn.2014-08.org.nvmexpress.discovery",
        "subtype": "Discovery",
        "listen_addresses": [],
        "allow_any_host": true,
        "hosts": []
    },
    {
        "nqn": "nqn.2016-06.io.spdk:cnode1",
        "subtype": "NVMe",
        "listen_addresses": [],
        "allow_any_host": false,
        "hosts": [],
        "serial_number": "1",
        "model_number": "SPDK bdev Controller",
        "max_namespaces": 32,
        "min_cntlid": 1,
        "max_cntlid": 65519,
        "namespaces": []
    }
]

[gbregman]

This is the as issue #145 which was fixed by #208. Now, when deleting a bdev you will get an EBUSY error in case there is a namespace still using it. If you pass the "--force" command line option, such namespaces will get automatically deleted and then the bdev will get deleted.