Remove Node class from NBD proxy

This was broken as part of the recent Node removal.  Although this code
is currently dead, it would be good if at least was able to be built, so
if someone was inclined to upstream the backend for it, they could
without too much trouble.

Because of this move in code, clang-tidy can now see this code and found
a number of failures, so this is combined with a couple of relatively
trivial clang-tidy changes that are low impact and mechanical in nature.

Tested:
Commented in the option in meson_options.txt, and built.  Code builds.

Signed-off-by: Ed Tanous <edtanous@google.com>
Change-Id: I5ff52b773fc4fc9d44a916c4e6bf6e60295c3aaa