staging/lustre/lnet: fix potential null pointer dereference in kiblnd_rejected

Null pointer 'cp' that comes from line 2544 may be dereferenced
at line 2618.
found by Klocwork Insight tool

Signed-off-by: Dmitry Eremin <dmitry.eremin@intel.com>
Reviewed-on: http://review.whamcloud.com/9386
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-4629


Reviewed-by: John L. Hammond <john.hammond@intel.com>
Reviewed-by: Isaac Huang <he.huang@intel.com>
Signed-off-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>