LU-8316 tgt: return -ENOMEM while kmalloc failed

LU-8316 tgt: return -ENOMEM while kmalloc failed

Return valid value in tgt_init().

Signed-off-by: Yang Sheng <yang.sheng@intel.com>
Change-Id: Iaaa3697aca42d84011886a360fb31576ed4b53df
Reviewed-on: http://review.whamcloud.com/20918
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Fan Yong <fan.yong@intel.com>
Reviewed-by: Alex Zhuravlev <alexey.zhuravlev@intel.com>
Reviewed-by: Bob Glossman <bob.glossman@intel.com>
Reviewed-by: Mike Pershin <mike.pershin@intel.com>
Reviewed-by: Dmitry Eremin <dmitry.eremin@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>