nvmet-passthru: propagate status from id override functions

The id override functions return a status which is not propagated to the
caller.

Fixes: c1fef73f ("nvmet: add passthru code to process commands")
Signed-off-by: Daniel Wagner <dwagner@suse.de>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Keith Busch <kbusch@kernel.org>