LU-7077 target: avoid using possible error return NULL pointer

LU-7077 target: avoid using possible error return NULL pointer

previous fix http://review.whamcloud.com/15576 added a call
to cfs_hash_getref().  add LASSERT() to ensure the can
never happen here return value of NULL is in fact never seen.

Signed-off-by: Bob Glossman <bob.glossman@intel.com>
Signed-off-by: Di Wang <di.wang@intel.com>
Change-Id: Ic6132b5450534db0bb9b89c3dd6f55517450c42a
Reviewed-on: http://review.whamcloud.com/16473
Tested-by: Jenkins
Reviewed-by: Dmitry Eremin <dmitry.eremin@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>