LU-1267 lfsck: enhance RPCs (2) for MDT-OST consistency

LU-1267 lfsck: enhance RPCs (2) for MDT-OST consistency

The LFSCK on the MDT uses LFSCK_NOTIFY RPC to control the LFSCK
on the OSTs (or other MDTs) to start/stop/fail/pause the layout
consistency verification. And uses LFSCK_QUERY RPC to query the
LFSCK status on the OSTs (or other MDTs).

Introduce new connection flag: OBD_CONNECT_LFSCK to indicate that
whether the target server (MDT/OST) supports online LFSCK or not.

Test-Parameters: allwaysuploadlogs
Signed-off-by: Fan Yong <fan.yong@intel.com>
Change-Id: Ia605f25d0ca0224af3ee543d72a1e9f0cae918e3
Reviewed-on: http://review.whamcloud.com/7087
Tested-by: Jenkins
Reviewed-by: Alex Zhuravlev <alexey.zhuravlev@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>