tcmu: clean up the code and with one small fix

Remove useless blank line and code and at the same time add one error
path to catch the errors.

Reviewed-by: Mike Christie <mchristi@redhat.com>
Signed-off-by: Xiubo Li <lixiubo@cmss.chinamobile.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>