nvmf: Switch several ioctls to using nvlists

[jhb]

Summary

For requests that handoff queues from userspace to the kernel as well
as the request to fetch reconnect parameters from the kernel, switch
from using flat structures to nvlists. In particular, this will
permit adding support for additional transports in the future without
breaking the ABI of the structures.

Note that this is an ABI break for the ioctls used by nvmf(4) and
nvmft(4). Since this is only present in main I did not bother
implementing compatability shims.

Inspired by: imp (suggestion on a different review)
Sponsored by: Chelsio Communications

[imp]

So I like this in general. And the few places that I checked the old/new code does the right thing as far as I Can tell by looking at it statically. I didn't audit everything though.
But that's likely OK if this passes whatever test-suite we have, imho.

[jhb]

The testing I did is to run a FreeBSD Fabrics controller on one test machine and the fabrics host on another and verified that I could still establish an association, do I/O, fail a connection, and then reconnect without blowing up anywhere.