LU-5417 tgt: incorrect return code from tgt_handle_lfsck_query

LU-5417 tgt: incorrect return code from tgt_handle_lfsck_query

Incorrect comparison of unsigned int with zero always false.
Therefore tgt_handle_lfsck_query() always return success.

Signed-off-by: Dmitry Eremin <dmitry.eremin@intel.com>
Change-Id: Idcb321880fb5071c93bebbba0a55961cdbe286dd
Reviewed-on: http://review.whamcloud.com/11290
Tested-by: Jenkins
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Fan Yong <fan.yong@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>