LU-6523 lmv: Error not handled for lmv_find_target

LU-6523 lmv: Error not handled for lmv_find_target

This issue is found by smatch; has been reported as-
Unchecked usage of potential ERR_PTR result in lmv_hsm_req_count
and lmv_hsm_req_build.
Added ERR_PTR in both functions and also return value check added.

Signed-off-by: Ulka Vaze <ulka.vaze@yahoo.in>
Change-Id: I9651bb70724a1b2f2a1901a3bf5093f84b22e6ea
Signed-off-by: Aditya Pandit <panditadityashreesh@yahoo.com>
Reviewed-on: http://review.whamcloud.com/14918
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Dmitry Eremin <dmitry.eremin@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>