LU-8450 nodemap: modify ldlm_revoke_export_locks

LU-8450 nodemap: modify ldlm_revoke_export_locks

Modify ldlm_revoke_export_locks to use cfs_hash_for_each_nolock
instead of cfs_hash_for_each_empty, to avoid looping multiple times
over the export hash.

Signed-off-by: Kit Westneat <kit.westneat@gmail.com>
Change-Id: I8ab475b8117493ed55961e94e747b4955141f003
Reviewed-on: http://review.whamcloud.com/23120
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>