LU-5128 obdclass: fix a race in recovery

LU-5128 obdclass: fix a race in recovery

in "class_export_recovery_cleanup", the check of the flag
"exp->exp_req_replay_needed" should be protected by "exp_lock".

Lustre-commit: 5a7e4480fc519c8df4ca0b11e6d5239956316bd3
Lustre-change: http://review.whamcloud.com/10849

Signed-off-by: Hongchao Zhang <hongchao.zhang@intel.com>
Signed-off-by: Wu Libin <lwu@ddn.com>
Signed-off-by: Jian Yu <jian.yu@intel.com>
Change-Id: Ib3c980101f400ce1b9cb0b3d2a4418fbec31b94b
Reviewed-on: http://review.whamcloud.com/11102
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>