LU-8935 ptlrpc: missing barrier before wake_up

LU-8935 ptlrpc: missing barrier before wake_up

ptlrpc_client_wake_req() misses a memory barrier, which may cause
strange errors.

Lustre-change: https://review.whamcloud.com/26583
Lustre-commit: 33033c27aae361069877d56d44714097a208aa76

Signed-off-by: Lai Siyao <lai.siyao@intel.com>
Change-Id: Ic8e9cbaf8c07f503798b95c608477508204d9614
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Wang Shilong <wshilong@ddn.com>
Signed-off-by: Minh Diep <minh.diep@intel.com>
Reviewed-on: https://review.whamcloud.com/28321
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: John L. Hammond <john.hammond@intel.com>