The following command:
```
echo /dev/sda | tee /sys/kernel/config/nvmet/subsystems/sda/namespaces/1/device_path
```
makes nvme_loop fail because fascinatingly, it adds an unexpected newline.
See:
```
/dev/sda
/dev/sda
1
tee: /sys/kernel/config/nvmet/subsystems/sda/namespaces/1/enable: No such file or directory
/dev/sda
1
```
Other distros don't have the same behavior:
```
CentOS 8
/dev/sda
/dev/sda
1
Ubuntu 20.04
/dev/sda
/dev/sda
1
```
Signed-off-by: Guillaume Abrioux <gabrioux@redhat.com>
Using an nvme loop device makes the LVs look like "real" disks,
which means we can exercise all of the normal code paths for
provisioning, deprovisioning, and zapping.
Signed-off-by: Sage Weil <sage@newdream.net>