staging: lustre: llite: check request != NULL in ll_migrate

staging: lustre: llite: check request != NULL in ll_migrate

Check if the request is NULL, before retrieve reply body
from the request.

Signed-off-by: wang di <di.wang@intel.com>
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-7396
Reviewed-on: http://review.whamcloud.com/17079
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Signed-off-by: James Simmons <jsimmons@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>