nvme-cli: ignore arguments that pass in "none"

nvme-cli: ignore arguments that pass in "none"

As we want to support discovery uevents over different
transports, we want to allow the kernel to provide missing
information in the form of none and have nvme-cli properly
ignore it.

One example is the host_traddr. If it is not set (which means
that the default route determined the host address) we will
want to do the same for newly discovered controllers.

So allow users to pass 'none' arguments as well.

Example:
  nvme connect-all ... --hostnqn=none --hostid=none --host_traddr=none

Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: James Smart <jsmart2021@gmail.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Reviewed-by: Minwoo Im <minwoo.im.dev@gmail.com>