nvmet-auth: return the error code to the nvmet_auth_host_hash() callers

If the nvmet_auth_host_hash() function fails, the error code should
be returned to its callers.

Signed-off-by: Maurizio Lombardi <mlombard@redhat.com>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Signed-off-by: Keith Busch <kbusch@kernel.org>