LU-1267 lfsck: enhance RPCs (3) for MDT-OST consistency

LU-1267 lfsck: enhance RPCs (3) for MDT-OST consistency

The LFSCK on the OST uses LFSCK_NOTIFY RPC to notify the LFSCK
on the MDT about the LFSCK progress for the layout consistency
verification. And uses the LFSCK_QUERY RPC to query the LFSCK
status on the MDT.

The LFSCK RPC from OST to MDT is sent via the reserse connection
from OST-x to MDT-y.

Test-Parameters: allwaysuploadlogs
Signed-off-by: Fan Yong <fan.yong@intel.com>
Change-Id: I138fa9b9ad8ab539379f25bb59ec04a1a482fddb
Reviewed-on: http://review.whamcloud.com/7108
Tested-by: Jenkins
Reviewed-by: Alex Zhuravlev <alexey.zhuravlev@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>