Addressed the comments from v2. I also added cleanup code to _nvmet_cleanup() to
make sure we do not leak resources when something goes wrong. I run into this
while testing and all tests after the first failure failed then.

The name of the patch series suggest that it switches to allowed_hosts
where it does that in 2 patches 11+12 out of 13 patches. The rest are
just bug fixes and unifications. It's true that any series will include
fixes, cleanups and prep patches, but this is too far :)

I'll let Shinichiro accept as he wish though.

The cleanups look fine to me.